Читать книгу Invasive Aliens - Dan Eatherley - Страница 10

‘This England never did, nor never shall,

Lie at the proud foot of a conqueror.’

The Life and Death of King John, William Shakespeare, 1623

They didn’t come for the weather, that was for sure. As Aulus Plautius knew only too well, gales, incessant rain and a fleet-destroying storm had scuppered Julius Caesar’s attempts to conquer the island in 55 and 54 BCE. But now, with orders from the new and already beleaguered emperor Claudius ringing in his ears, the general had no choice but to try again. So, when the first Roman caliga squelched into British mud somewhere along the southeast coast in 43 CE, there was a new determination to get the job done and, with 40,000 legionaries, auxiliaries and cavalry troops at his disposal, Plautius could hardly fail. Yes, some opposition would need to be dealt with. Caractacus, chieftain of the Catuvellauni people, was routed at the battle of Medway and his stronghold at Camulodunum – present-day Colchester – seized, but he fled to the west to fight a prolonged insurgency before his eventual capture. A few years later Boudica, the Iceni queen, also had a pop at the invaders, razing Camulodunum, along with Londinium (London) and Verulamium (St Albans). But she, too, succumbed. Rome would never conquer the entire island; however, within a century much had been brought to heel, with the Scots and other recalcitrants left to their own devices.

What Britannia lacked in climate and hospitable welcome was more than offset in mineral wealth: iron in Kent, silver in the Mendips and a generous seam of limestone from Oxfordshire to Lincolnshire, perfect for building roads and towns, aqueducts and bath-houses. Productive agricultural land was widespread too, although scant forest remained. Nevertheless, like all colonists, the Romans felt their new possession wasn’t quite up to scratch.

The food in particular left much to be desired. Little in the way of fruit and veg was grown in Late Iron Age Britain. Notwithstanding the odd amphora of wine, olives, shellfish and other rarefied menu items that some pre-Roman elites are known to have imported, the locals had to content themselves with a diet heavy in oats and barley. A modest range of vegetables was cultivated, but dairy products were seasonal treats and meat a luxury. Most of today’s familiar herbs and spices were absent. For the Romans, this just wouldn’t do. Oats and barley were all very well for the subjugated – or as livestock fodder – but their own tastes were more refined.

The occupying power set about expanding the cuisine, introducing at least 50 new species of plant foods, most originating in the Mediterranean Basin. These included fruits such as peach, pear, fig, mulberry, sour cherry, plum, damson, date and pomegranate, along with almond, pine nut, sweet chestnut and walnut. Romans brought vegetables too, from cultivated leek and lettuce, to cucumber, rape and possibly turnip, along with new varieties of cabbage, carrot, parsnip and asparagus which already grew wild in Britain. Black pepper, coriander, dill, parsley, anise and black cumin added to a bonanza of outlandish flavours. Oil-rich seeds of sesame, hemp and black mustard were also among the arrivals.

Many introductions had supposed medicinal functions too. For the Roman historian, Cato the Elder, the cabbage surpassed all vegetables in that respect. Writing in about 160 BCE, he noted that it ‘promotes digestion marvellously and is an excellent laxative’. Moreover, he insisted, there was nothing better than a warm splash of urine collected from a habitual cabbage-eater to treat headaches, poor eyesight, diseased private parts and sickly newborns. Another plant introduced to Britain for its therapeutic properties was Alexanders – the ‘parsley of Alexandria’ – a chunky lime-green relative of celery, which grew to 150 centimetres in height and was prized as aromatic vegetable and versatile tonic alike. The Romans may have been on to something here: recent chemical analysis of Alexanders reveals high concentrations of the anticancer compound isofuranodiene.

How many of these species were grown in Britain during the occupation rather than imported as ready-to-eat crops is unclear. The sweet chestnut, for instance, a staple of many a legionary’s mess-tin, is absent from the medieval pollen record, suggesting it was grown here only much later. A period of hotter summers across northern Europe, including Britain, during the early years of Roman occupation may have favoured the growth of warmth-loving figs, mulberries, grapes, olives, pine nuts and lentils, albeit on a modest scale, perhaps in garden pots. By the time the Romans left, several introductions, including walnut, carrot and cherry, are known to have fully established themselves.

The origins of certain plants can be traced to Britain’s first formal gardens, laid out during the Roman period. The best-known example is Fishbourne Palace in West Sussex, built in about 75 CE, whose outdoor space boasted tree-shaded colonnades and ornamental water features, along with geometric beds, fertilised with manure and bordered by a decorative hedging box. Fishbourne is now believed to have been the residence of a loyal Brit: Tiberius Claudius Cogidubnus, chieftain of the Regni tribe; if true, it was a handsome reward indeed for his allegiance to the occupying power.

A minority of Roman plant introductions are today regarded as invasive. One of them is probably ground-elder. This iron-rich perennial was cultivated both as culinary herb and for treating arthritis (another name for it is ‘gout weed’), but once its spaghetti-like rhizomes got a foothold, ground-elder was near unstoppable. (Rhizomes are specialised subterranean stem sections capable of putting out both roots and new shoots.) To this day, up to £1 million is spent every year eradicating it from gardens. Some experts say ground-elder is native, but because the weed is usually found close to human habitation its presence here is generally blamed on the Romans.

As we’ve seen, sheep, cattle, pigs and goats were established in Britain prior to 43 CE, but the chicken – today the world’s commonest and most widespread livestock species – was still a rarity in this country, judging from its absence in the archaeological record. This may have been an artefact of the poor preservation of their brittle bones and difficulties in identification. The earliest remains appear in Early Iron Age burial sites (around 800 BCE), in Hertfordshire and Hampshire, and their very scarcity may have perhaps been reason enough to entomb these exotic birds from the Orient with the lately departed. But when, where and why were people first drawn to the red junglefowl, the chicken’s probable wild predecessor? No one knows for sure, but domestication seems to have occurred somewhere in south or southeast Asia around 4,000 years ago, with tame fowl brought to the Mediterranean by the eighth century BCE, reaching central Europe a hundred years later.

Chickens and their eggs have always been eaten, but for much of human history they’ve been as prized for their pugilistic prowess as for their gastronomic qualities. Cockerels, it turned out, need scant encouragement to set at each other with beak, claw and, in the older birds, wickedly sharp leg spurs. The skirmishes have excited the bloodlust of onlookers for generations. Cockfighting spread west across India and the Middle East, the sport in turn captivating the Persians, Greeks and the Romans. Chickens held a religious significance too, the males symbolising the sun god in the Roman cult of Mithras. Caged fowl would be taken on military campaigns and their eating habitats studied for purposes of divination; if your sacred chicken, when offered food, guzzled it down, all augured well for the impending battle. Fowl-keeping in Britain grew in popularity up to and throughout the Roman invasion, albeit the preserve of a privileged few. Here, as elsewhere, chickens were multifunctional, a source of food, entertainment and devotion. Their bones are associated with Roman temples, such as one at Uley in Gloucestershire dedicated to Mercury, and they regularly turn up in Romano-British graves.

Various other animals were imported for nutrition, status and religious reasons, with the remains of pheasant, peafowl, guinea fowl and donkey all found occurring in Roman sites. Elephants were the most impressive creatures brought to Britain; the Emperor Claudius used them to intimidate his new subjects soon after his victory – their stink had the added benefit of panicking enemy horses – although the tuskers’ visit seems to have been fleeting. Archaeologists are intrigued by the discovery at Fishbourne and on the Isle of Thanet, Kent, of numerous bones of fallow deer, a variety hailing from the Anatolia region of modern-day Turkey. Analyses of the deer teeth at both sites indicate well-established, breeding populations, a finding that hints at the existence of what might turn out to be Britain’s earliest deer parks.

As with so many non-natives, the story of fallow deer is far from straightforward since they vanished with the Romans around 400 CE. It was long assumed that the species only returned to Britain with the Normans, but recent radiocarbon dating work suggests they were around just before the Battle of Hastings. Either a few of the Roman deer hung on in the wild, or more likely, small-scale reintroductions, perhaps as novelty items, continued to occur over the course of succeeding centuries.

Sometimes creatures were kept for company alone. That seems to be true both for natives, such as ravens and crows, which were popular pets among the soldiers in Iron Age and Roman Britain, and for the more exotic. Examples of the latter included the Barbary macaque, a monkey whose bones have been recovered from Roman sites at Wroxeter, Dunstable and Catterick.

The Romans weren’t averse to the odd invertebrate too, notably snails, new species of which were introduced as a delicacy. The pot lid, or Burgundy snail remains the most popular of several edible types that now support a multi-million-pound global escargot market. These days snails are largely absent from menus this side of the Channel, where they are regarded as vermin. Indeed, the 5,000 tonnes of molluscicide applied every year to keep them at bay could fill two Olympic swimming pools.

Most creepy-crawlies arriving and spreading during Roman times came unnoticed as hitch-hikers, such as grain weevils. The earliest British remains of these and other insect pests of food stores show up at sites in London and York dating to within the first decades of the Roman occupation, suggesting that infested grain was imported from Europe soon after the invasion. Invertebrate parasites of livestock and people flourished as new forts, towns and cities sprang up, and human population density grew. The Romans were known for their close attention to personal hygiene, with flushable latrines and heated bathwater. Yet, these measures failed to arrest the proliferation of tapeworm, liver flukes, roundworm and whipworm, along with swarms of fleas, lice and the odd bed bug. The widespread prominence of fish tapeworm, a gut parasite attaining nine metres in length, is something of a puzzle since the species is rarely evidenced in earlier, Bronze and Iron Age sites. Here, the Roman weakness for a peculiar condiment called garum may have been the cause. This fermented sauce, a blend of raw freshwater fish and herbs, left to rot in the sun, was traded across the empire and could have helped spread fish tapeworms.

From the late fourth century, the Roman Empire began to wither. Soldiers stationed in Britain were recalled to fight insurgencies on other fronts and by 410 CE the northern outpost had been abandoned. What happened over the next six centuries, traditionally dismissed as the Dark Ages for the paucity of written records, is vague. Roads and other imperial infrastructure disintegrated, vibrant towns and cities decayed, and trade declined, all slowing the influx and spread of new species. Yet, this was a period of great human churn as populations from Ireland, Scotland and other outlying regions of the British Isles moved into undefended territory, joined by continental immigrants, particularly from Scandinavia, the Netherlands and Germany. These movements of Angles, Saxons, Jutes and other peoples would have instigated fresh introductions, deliberate and accidental, but for now the details are lost in time.

The elite are always keen to improve upon what nature has provided and, when it comes to reshaping and enhancing the landscape, few matched the enthusiasm of the Norman invaders of 1066. With a mania for hunting, Britain’s newest overlords depopulated large tracts of territory in the interests of blood sport. Dozens of hunting grounds, or ‘forests’, were designated, encompassing not just wooded areas but moorland, cultivated fields, and even whole villages, from which the occupants were banished under ‘forest law’. Any animals which could jeopardise the chase were also dealt with with ruthless efficiency: sheep and goats, whose grazing could damage the forest vegetation, were removed, and unwanted dogs hobbled in a procedure known as ‘lawing’, which saw the claws from one foot lopped off with mallet and chisel. The Anglo-Saxon Chronicle for 1087 implies that William the Conqueror’s focus was native game: ‘Whoever slew a hart or a hind [male or female red deer] was to be blinded. He forbade the killing of boars even as the killing of harts. He loved the harts as dearly as though he had been their father. Hares, also, he decreed should go free.’ Yet, William and his successors seemed happy to bring in, and protect, foreign quarry species.

This included the fallow deer. Like the indigenous red deer, fallow offered fabulous sport for the mounted hunter and hound by galloping away across the countryside. (The roe, Britain’s other native deer, was far more skittish and a bit of a killjoy: its instinct was to hunker down in thick undergrowth at the least sign of danger, and it could even die of fright.) As discussed, small numbers of fallow deer may already have been present in Britain before the Normans; certainly, by the beginning of the twelfth century the species is known to have been well established. There’s also a possible Sicilian connection here.

After a 30-year campaign, the Normans completed their capture of this Mediterranean island from the Arabs in 1091. Perhaps impressed by the parks of wild animals, including fallow deer, kept by Sicily’s previous rulers, in 1129 King Henry I had 11 kilometres of wall built around his own estate at Woodstock, Oxfordshire, to which he introduced lions, leopards, camels and a porcupine. And fallow deer. According to the archaeologist Naomi Sykes, ‘This collection, which is the direct ancestor of London Zoo, was not simply a frivolity; it was a metaphor for the Norman Empire, a statement that the Norman kings had power not only over the wild creatures in their possession but also over the countries from which the animals derived.’ In addition to being far more manageable than red and roe – their scientific name Dama comes from the Persian for ‘tame’ – fallow thrived on poor quality land, so proved an immediate hit. By the 1300s, the deer had been stocked in some 3,000 parks across Britain; in England alone, these enclosures covered the equivalent of 2 per cent of the entire land area. The modern distribution of fallow deer, whose UK population probably exceeds 200,000 individuals, matches that of the medieval parks from which they escaped. (According to Charles Smith-Jones of the British Deer Society, fallow are remarkably loyal to their home areas and seem inclined to heft strongly to them.) Like other deer species – both native and introduced – the fallow is today regarded as a crop pest, an unwitting cause of vehicle collisions, and a potential carrier of disease from bovine tuberculosis to foot-and-mouth.

The common pheasant was already successful before its introduction to Britain, having colonised a swathe of Eurasia from the western Caspian region to Japan. As discussed, in Britain its bones first turn up at Roman sites, and historical documents – most of them written after the fact – indicate that pheasants were sometimes eaten as a luxury prior to the Norman invasion. For instance, in 1059, King Harold is said to have offered the bird as a privilege to the canons of Waltham Abbey in Essex, a gift deemed equivalent in value to a brace of partridges or a dozen blackbirds. In 1098, Radulfus, the Prior of Rochester, dispatched to his monks 16 pheasants (along with 1,000 lampreys, 300 hens, 30 geese, 1,000 eggs, 4 salmon and 6 bundles of wheat). A contemporary and perhaps more dependable record – a bursar’s roll at Durham Priory dated to the reign of the Saxon king Edward the Confessor (1042–1066) – includes a purchase of one pheasant and 26 partridge. Pheasants may first have been kept in royal parks and forests, along with fallow deer, and their increasing prominence on banquet menus from the late twelfth century implies that they had by then naturalised. In 1251, Henry III ordered 290 of them for his Christmas feast, and by the late 1400s, pheasants warranted legal protection from the Crown. These early imports were in fact the ‘Old English’, or colchicus, subspecies from the Caucasus and lacked the distinctive white neck ring of the torquatus race, originating in China, which is these days released for shooting.

The pheasant is something of an outlier from this period in retaining a certain aristocratic association. The best explanation is that these poorly camouflaged, clumsy fliers have so far failed to get along in the British countryside, despite repeated reintroduction. Of an estimated 20 million poults (young birds) loosed annually, 90 per cent perish within the year. And not just from the shooting: most evade the guns only to be picked off by foxes or end up as roadkill.

Although pheasants might one day naturalise in Britain, there’s precious little evidence for that so far. The same can’t be said for what is without doubt the most impactful of all medieval introductions.

‘It’s quite a massive hill here, this site,’ I said. ‘And that’s all just made for the rabbits, this big mound?’

‘Well, no. The hill, I think, is natural. It’s just that rectangular mound there that’s made for them,’ responded David patiently.

‘Sorry. I was thinking the whole hill was a warren!’

‘Oh. That would make it the world’s biggest pillow mound, yeah.’

The aroma of wood smoke wafted in the chilly morning air. A distant chainsaw whined. We were standing at the foot of a steep grassy hillock, almost 100 metres high, upon which was broodingly perched a three-storey tower of limestone. Known these days as the Bruton ‘dovecote’ for its later repurposing by pigeon-fanciers, the original function of the pale-yellowish structure, which dates back to the 1500s, is a mystery. One theory has it as the prospect tower for the nearby Bruton Abbey – long since demolished on the orders of Henry VIII during his dissolution of the monasteries – offering the local aristocracy a grandstand view of the abbey’s deer park. But neither doves nor deer, nor indeed the pair of Friesian cows munching contentedly near the base of the tower, had drawn me to South Somerset today.

No, I was interested in rabbits and in particular how and why these shy burrowing mammals from southwest Europe had been introduced to Britain, and then run amok. An important clue was offered by the pillow mound, a characteristic earthwork which to the trained eye shouts ‘rabbit’. Clearly, my eye wasn’t trained because Dr David Gould, a landscape archaeologist from the University of Exeter who had agreed to show me some, needed to point out the example that was right in front of us.

‘You see that ridge coming down the hill?’ he said. ‘That’s one.’

The British population of the European rabbit today numbers in the tens of millions and the species is now regarded as a worldwide menace. Yet the original bunnies were an ineffectual lot, hardly a patch on their vigorous descendants and quite unable to excavate their own burrows. This is where the pillow mounds came in. Created by piling up soil in long, low heaps, and encircled by ditches, possibly to deflect any floodwaters, these artificial structures provided a dry, soft and well-ventilated substrate into which the rabbits could dig. Some even incorporated stone-lined tunnels making life easier still for their feeble tenants. At the same time, pillow mounds concentrated the rabbits in one place for ‘hunting’. If you could call it that. The phrase ‘shooting fish in a barrel’ comes to mind.

The pillow mound was a hallmark of the artificial rabbit warren, or ‘coneygarth’, from the Middle English coning-erth. Coney, coning, conyng, and sundry other derivations thereof, was the original word for the adult animal, the term ‘rabbit’ – from the French rabette – being reserved for juveniles. David had spent three years visiting 650 coneygarths across southwest England, from Cornwall to Wiltshire, racking up more than a thousand pillow mounds along the way. Little wonder he knew one when he saw it.

‘Most are rectangular, like the ones here at Bruton,’ he said. ‘But you get circular ones, oval ones, cruciform ones. Just random, weird little ones.’

I suspected pillow mounds haunted his dreams.

Along with documenting the shapes, David was keen to understand just how conspicuous the pillow mounds were: ‘If you were wealthy, you were expected to have access to these animals. It was kind of like the “in thing”. But I wanted to know whether pillow mounds themselves, as visual components of the landscape, had a symbolic significance in their own right. Was it like parking your expensive car in the front drive to show off?’

In the event, David’s field work revealed no clear pattern: pillow mounds were as likely to be tucked away behind a hill as to be sited ostentatiously on its slopes. It seemed that so long as the lord of the manor could offer distinguished guests fresh rabbit for dinner, whether or not the warren was visible from the manor house was of little concern.

As with other exotic imports, rabbits served multiple functions, offering meat, fur and status. Like pheasants and fallow deer, the association with elites can be traced as far back as the Romans who, elsewhere in their empire, prized rabbit foetuses, known as laurices, as a delicacy and reared the creatures (along with hares) in stone-walled pens called leporaria. The discovery of a fragment of rabbit tibia at Fishbourne, dated to the first century CE, suggests the species was brought to Britain during the Roman occupation, perhaps as a pet. But rabbits don’t seem to have established: there’s no Anglo-Saxon word for them and they don’t get a nod in the Domesday Book. ‘Coney culture’ nevertheless persisted on the continent after the Romans left and, by the Norman period, rabbits had been added to the variety of smaller game that aristocrats would seek permission from the king to hunt under the right of ‘free warren’. (Other free warren species – undoubtedly offering more sport – included fox, hare, wildcat, pheasant and partridge.)

Britain’s current rabbit population dates to the second half of the twelfth century, with animals possibly brought by homeward-bound crusaders. At first, the rabbits were kept on islands off the south coast of England, the benign climate and lack of predators suiting these delicate mammals. Although there’s some dispute about it, the earliest putative record dates to around 1135 when Drake’s Island in Plymouth Sound was said to have been granted to Plympton Priory, cum cuniculus (‘with rabbits’). In 1176, rabbits were being kept on the Scilly Isles, while on Lundy in the Bristol Channel, the tenant was permitted to take 50 a year between 1183 and 1219. One of the earliest allusions to mainland rabbit-keeping dates to 1235 when King Henry II presented ten live coneys as a gift from his park at Guildford.

Soon after the introduction of rabbits to mainland Britain, coneygarth escapees were turning up as pests on nearby arable fields, yet the species remained scarce during the early years. This rarity was reflected in the price, with a single animal costing the same as five chickens. Coneygarths were guarded and poachers subject to the full weight of the law. In England alone, 465 cases of rabbit theft are recorded between 1268 and 1551. Contrary to popular belief, peasants weren’t always – or even mostly – responsible for rabbit-thievery. Break-ins were more often than not the handiwork of fellow landowners in a spirit of aristocratic one-upmanship. Warreners, who were tasked with ensuring the safety of their precious charges, had their work cut out. They constructed lodges and watch-towers to spot poachers, and fitted ingenious vermin traps to divert and capture stoats, weasels and other would-be predators. Trowlesworthy Warren on Dartmoor, which dates back to the seventeenth century, boasted 76 such traps. But not every rabbit predator was quite so unwelcome.

The ferret, a tame version of polecat which originated in North Africa and had been domesticated since the fourth century BCE, appeared in Britain from 1223, soon after the dawn of rabbit-keeping. Warreners co-opted the wiry carnivore to their cause, filing down its teeth and using it to flush bunnies from their burrows. Ferrets also formed an important component of the rabbit-poacher’s toolkit, along with dogs and nets.

Against the odds, the rabbit population started rising, and by the fourteenth century supported a growing export trade in their furs; in 1305, for instance, 200 skins were shipped out of Hull, and by 1398 a certain Collard Chierpetit was granted the right to send 10,000 rabbit pelts to Holland. No fewer than 4,000 rabbits were served at the 1465 investiture of the Archbishop of York and, a century later, the Swiss naturalist Conrad Gesner noted that: ‘There are few countries wherein coneys do not breed, but the most plenty of all is in England.’ It wasn’t until the late 1700s, however, that the wild population properly took off; rabbits had by then evolved into an altogether hardier proposition, able to capitalise on new rotational field systems, which provided a year-round supply of food. The wholesale removal of weasels, pine martens, polecats, stoats, foxes and other predators by gamekeepers tasked with preserving pheasant and partridge, also indirectly benefited the rabbit whose ubiquity helped consign their high-class status to history. Rabbit farming continued in Britain right up to the twentieth century, with numerous large coastal semi-natural warrens in places like Cornwall and South Wales continuing to be protected from poachers, suggesting that the species retained a certain economic value until modern times. Nevertheless, this once-prized commodity fit for a king generally came to be dismissed as a pauper’s ration, and at worst, vermin to be eradicated.

Rabbits have long had religious connotations, most likely anchored in the supposed proclamation of the sixth-century Pope Gregory that rabbits, or more precisely their foetuses, were fit for eating on fast-days. Plucked from the womb’s watery environment, the reasoning went, laurices could be deemed honorary fish, not warm-blooded animals which would have been off limits. But this turns out to be a case of sloppy scholarship: the Pope never made any such decree. Instead, it was his contemporary and namesake, Bishop Gregory of Tours who had pronounced on rabbits, and merely to report on the practice of laurice consumption during Lent. Chinese whispers did the rest.

Writing in the 1990s, the archaeologists David and Margarita Stocker nevertheless detected an allegorical significance in ‘defenceless’ communities of rabbits being ‘herded and managed like sheep’ by a Christ-like warrener, before emerging ‘from the ground to fulfil themselves’. Warming to their theme, the Stockers evidenced the deliberate, prominent and ‘symbolically meaningful’ placement of pillow mounds within monastic precincts at Sawtry Abbey in Cambridgeshire, Nun Coton Priory in Lincolnshire and Croxton Abbey in Leicestershire. In his own documentary research on rabbits, however, David Gould has found little to bolster, or at least privilege, the sacred connection. ‘In the medieval period it’s basically the elites who first owned rabbits,’ he said, ‘and that meant both lay and clerical elites. In fact, when you look back through the records, warrens are more often linked to secular aristocracy.’

As it happened, Bruton had something to say on fish too (another reason David had suggested we meet here). We trudged to the crest of the dovecote-dominated knoll which gloried in the name of ‘Lusty Hill’. Was this a reference to the renowned reproductive capacity of its former livestock? That was a question for another day. Passing two smaller pillow mounds on the summit, we descended the far side to a series of boggy depressions, the remains of ancient and overgrown ponds. ‘I’m not an expert, but I think they’re medieval and older than the pillow mounds,’ said David. These artificial pools – fed by a stream which flows on to the River Brue – once supplied fresh fish to Bruton Abbey.

Whether or not rabbits were regarded as fish and kept and eaten for their ecclesiastical significance is unclear, but actual fish certainly were favoured by religious orders across continental Europe and, between the ninth and eleventh centuries, appeared ever more prominently on the table at Benedictine monasteries. The stricter regimes at Cistercian and Carthusian communities resisted even fish but later allowed the consumption of small quantities, or ‘pittances’. The medieval period coincided with a massive expansion of marine fishing which targeted herring, cod and hake. While coastal communities enjoyed fresh catch, those living far inland had to make do with salted or dried fish. The elites, though, abhorred preserved fish and instead focused on locally caught freshwater species, like eels, which were trapped as they migrated up or downstream. The younger specimens were grown in stock ponds, either purpose-built or adapted from existing millponds, moats and former river channels.

Meanwhile in Britain, the eating of fish also grew in popularity in the centuries following the Norman Conquest. The people of this island nation had always enjoyed access to seafish, but the continental pond culture centring on freshwater varieties was nevertheless imported, as much for its prestige as for its nutritional benefits. Like deer parks and coneygarths, Britain’s fishponds were first associated with the wealthy, and by 1300 could be found on the estates of clergy, aristocratic landowners and the Crown from Wiltshire to Yorkshire – the ones at Bruton being surviving examples. In time, husbandry techniques advanced enough to provide a steady food source and aquaculture became a widespread commercial enterprise, although freshwater fish retained its cachet. The sorts of fish best able to endure the warm, slow-moving, turbid and oxygen-poor water of medieval ponds were favoured. That meant roach, tench, chub, dace, perch, and especially pike and bream. To this roll-call of hardy natives would later be added a foreign fish whose origins are as murky as the waters it frequents.

The common carp is today among the world’s most important food fishes. Three million metric tonnes are grown annually across 100 countries, equivalent to a tenth of all freshwater aquaculture production. It’s easy to see why: the fish breeds and grows fast, tolerates a wide variety of environmental conditions and eats pretty much anything that can be sucked up by its telescopic mouthparts. The koi carp, a colourful variant developed in a mountainous region of Japan, is perhaps the world’s most popular outdoor ornamental fish and almost as well travelled as its edible cousin. Meanwhile, the species supports an angling market which in Britain alone is worth close to a quarter of a billion pounds each year.

The ancestral common carp evolved close to the Caspian Sea around 2.5 million years ago and, taking advantage of the proliferation of waterways during warmer interglacial periods, expanded its range east into mainland Asia and west to the basins of the Black and Aral Seas. The European version of the common carp appeared in the Danube river some 10,000 years ago. And there the fish might have stayed were it not for its discovery by the Romans – keen aquarists – sometime in the first or second century CE. (Carp bones dated to that period have been identified at the site of a former Roman frontier fort near Iža in Slovakia.) Able to survive out of water and without food for prolonged periods, the carp were transported, possibly wrapped in wet moss or sacking, to the piscinae (reservoirs) of Italy as gourmet items and pets.

Carp however, live specimens at least, weren’t present in Roman Britain, and don’t feature in European pond culture until around the twelfth century. The first written reference on this side of the Channel comes from the kitchen accounts of King Edward III at Canterbury, dated to 1346, which show a carp and eight pike costing 22 shillings. The carp in this case was probably an imported specimen, because the fish doesn’t seem to have been stocked in this country for another century. In 1496, The Boke of St Albans – attributed to Dame Juliana Berners, prioress of Sopwell nunnery – describes the carp as a ‘deyntous [delicious] fisshe’, and then in 1532 ‘Carpes to the King’ appears in Henry VIII’s Privy Purse expenses for that year.

Despite this, carp was historically less important in Britain than elsewhere, perhaps because by the sixteenth century improvements in navigation and ship technology were, for the first time, allowing exploitation of vast new shoals of marine fish from offshore Atlantic waters. The common carp nevertheless qualifies as among the first non-native fish to have naturalised in Britain and remains abundant in still and slow-flowing waters across England, with scattered populations in Wales and Scotland. The species is often accused of muddying the water as it ploughs river and lakebeds for invertebrates, fish eggs and other buried morsels. The resulting high water-turbidity stops light penetrating and interferes with photosynthesis, messing up food webs. But carp enthusiasts, of which there is a growing army in Britain, argue that recreational boating and other human activities are as much to blame.

A fascination for all things botanical, both native and exotic, also germinated within the monasteries and aristocratic households of Britain during medieval times; commercial horticulture can be traced to the thirteenth century, with enterprises in London and Oxford selling seeds in large numbers. Husbandry, a set of rules for estate management by Sir Walter of Henley published in 1280, states that imported corn-seed often outperforms home-grown counterparts, and this influential work may have encouraged the acquisition of foreign plants. By the late 1300s the Dominican friar and herbalist Henry Daniel was nurturing 252 sorts of herb in his garden in Stepney, London, of which 100 were non-native.

Plants were cultivated primarily for function not aesthetics, although the beauty of snapdragons, snowdrops and snake’s head fritillaries – all of them apparently introduced during this period – is undeniable. Dill, coriander, summer savory, black mustard, fennel, caraway and parsley were all condiments whose use had declined after the Romans left but which made a big comeback during medieval times. Hitherto unknown species also arrived including saffron, a luxurious yellow spice made from the dried stigmas of a crocus flower. The plant originated in western Asia and is first recorded in England in the fourteenth century. Used as culinary ingredient, dye, perfume and aphrodisiac, saffron was famously grown in East Anglia, its economic significance such that a major centre of production, the Essex town of Walden, adopted it as a prefix in the sixteenth century.

Horticultural introductions served other purposes. As its name suggests, the leaves and roots of soapwort, a member of the pink family native to the Middle East, contain natural detergents. Appearing in Britain from medieval times, soapwort found use in the wool trade, washing not just woollen products but the sheep from which they were derived; as recently as the 1970s, extracts were employed to clean fragile tapestries. Chasteberry, a type of vervain with purple flower cones which originates in the eastern Mediterranean, was used in monasteries to suppress libido among the acolytes, and nuns stuffed their bedding with the aromatic leaves to quash wicked urges. (The ancient Greeks prized the plant for the reverse effect: women slept on it to enhance their fertility.) The Aegean wallflower, meanwhile, was esteemed for the fragrance of its vivid golden blooms, reminiscent of violets. In its home range, the plant spreads over cliffs, and may have first reached Britain stuck to building stone imported by the Normans. It’s still found clinging to ancient edifices from Bury St Edmunds Abbey in Suffolk to Northumberland’s Lindisfarne Priory.

Almost every introduced plant offered some or other kind of therapeutic function. Gout was treated with wall germander, a variety of mint; feverfew, in the daisy family, was a traditional painkiller; hollyhock, a laxative. Many plants were considered panaceas. Sweet cicely, a celery relative whose strong scent called to mind myrrh, was one of countless such ‘cure-alls’ and was used to remedy rheumatism, cleanse cuts and salve sore throats. It could relieve asthma, cure snakebite and promote sleep. Sweet cicely even stopped you farting. From time to time, serious mistakes could be made: to medieval midwives, the pretty yellow flowers of birthwort, a variety of clematis, resembled wombs – one shudders to imagine how they would know that – and they would administer its sap during labour to expel the placenta. It turns out that birthwort extracts are carcinogenic and may have killed thousands of women over centuries of misuse.

Such cases were rare however, and did little to disillusion medieval herbalists. Yet, in the fourteenth century there arrived in Britain a disease – caused by one non-native and apparently carried by others – which even sweet cicely would be powerless to prevent (although people gave it a go). It would help change the course of human history, disrupting existing power structures and kick-starting an era of empire building and world exploration to dwarf anything achieved by the Romans and Normans. And the unprecedented globalised trade and migration that resulted would turn a trickle of non-native species into a deluge.