On 25 December 1406, the Bishop of Salisbury sat down for his Christmas dinner. Now an elderly man, Richard Mitford had led a wild life of dramatic highs and lows – at one point he served as a senior member of Richard II's royal household, and at another, he was imprisoned in the Tower of London for treason.

But now Mitford was in his twilight years, and having a jolly old time.

The meal was a modest affair by the Bishop's usual standards – there were only 97 people invited. On the table was a carpet of food so extravagantly carnivorous, it was almost the contents of a whole zoo. This included half a cow, three sheep, 24 rabbits, a pig, half a wild boar, seven piglets, two swans, two woodcocks, four mallard ducks, 20 snipes (long-beaked wading birds that bleat like goats), 10 capons (castrated cockerels), and three teal ducks.

That year, Christmas Day fell on a Saturday – a day of worship when people were technically only supposed to eat fish. So His Excellency ordered in some of this as well. In all, the guests were served 50 white herrings (pickled, a bit like rollmops), 50 red herrings (herring so heavily salted, it turns coppery-red), three vast conger eels, 200 oysters and 100 whelks.

Back then, there were no forks and people didn't have individual plates at a meal – the former hadn't turned up in England yet, and the latter wouldn't be invented until the 17th Century. With only knives and spoons at their disposal, Mitford and his guests ate everything either sliced or ground up, so that it could be served on flat, rounded pieces of bread called "trenchers".

“There's a great deal of ceremony that goes with this," says Chris Woolgar, an emeritus professor of history and archival studies at the University of Southampton, who has studied Mitford's culinary habits extensively. "These are prestigious foods to be displayed," he says, explaining that there would be dedicated carvers there, to pile food onto the guests' plates.

But there was one meat Mitford's Christmas menagerie did not contain: a glistening dome of roasted turkey. In fact, the dish wouldn't appear in England until decades later – and only became a staple in the early 20th Century. With the whole wide world of other meats to choose from, how did these strange birds from Mexico eventually become a festive staple? And which ancient Christmas delicacies did they supplant?

Woolgar first stumbled upon Mitford when he was working as an archivist at the University of Oxford in 1979. At the time, he was cataloguing the domestic accounts of large households – records in which the culinary expenditures of lords, ladies and bishops are outlined in tantalising detail. He quickly realised the rich insights they could provide into medieval life, and wrote up his findings in a book, The Culture of Food in England, 1200-1500.

"They describe, day by day, what people are buying and what they're consuming," says Woolgar.

For example, Mitford's accounts revealed how astonishingly varied his diet was – in just one year, he consumed 42 different kinds of fish, including thornback rays, whitebait, bass, carp, cod, crayfish, eel, gudgeon, haddock, hake, mackerel, lampreys, mullet, perch and pike.

But though lords and ladies had always had it good, in the late 14th Century one aspect of life – including Christmas – had recently been improved for everyone. It was all down to an unexpected side effect of a global tragedy: the Black Death.

Before this, most people would have survived primarily on cereal-based foods such as bread and "frumenty", a kind of porridge made from boiled cracked wheat with milk or stock.

"There's very little in the way of protein in the diet in terms of dairy or eating meat," says Woolgar, pointing out that many people survived on donations from wealthy families or alms houses. The wife of one exchequer official in Norfolk provided food for 13 peasants each day – a number carefully chosen for its Christian symbolism – though this consisted exclusively of bread and herring.

But when the Black Death ripped through Europe, Asia and North Africa in the mid-14th Century, it wiped out 30-40% of the population on the entire planet. Those who were left behind found that there was a lot more food to go around. "It's a pandemic that kills people, not animals. So the balance changes quite markedly from that point onwards," says Woolgar. Suddenly, meat was back on the menu for the masses – and everyone wanted to eat like a lord or lady at Christmas.

One of the most popular meaty centrepieces for Christmas feasts in the Middle Ages is thought to be ancient – a pickled boar's head. The dish is thought to have been extremely laborious to make, and was usually presented with an apple in its jaws and elaborate herbal decorations. It was so beloved, it even came with a song: the Boar's Head Carol, which was sung as it was processed into the room on a platter. In wealthy households, the tune would have been performed by minstrels – medieval entertainers – and heralded by trumpets.

However, despite the dish's popularity – it's widely depicted in Christmas scenes from the era – how it was actually made is less clear. What is certain is that is would have been a grisly process.

The finished dish is said to have tasted like a particularly delectable pork pie, and was often served along with "brawn" – meat from the boar's shoulders which was preserved in cider, wine or vinegar.

However, though the boar's head and its carol have long been forgotten by the general public, it lingers on in one institution to this day. Oxford University's Queen's College has held the Boar's Head Gaudy – a feast complete with a pickled boar's head and the traditional carol sung by a full choir – for centuries. It was originally started as an ordinary Christmas feast for college members who remained during the holidays, and has since evolved into an annual celebration on the Saturday before Christmas.

In 1526, a young Yorkshire landowner returned to England from a long trip. William Strickland had sailed to the New World on a voyage of discovery, where he purchased six rather silly-looking birds from Native American traders. They had wobbly flaps of skin that flopped over their beaks like red socks, and liked to strut around with their tails fanned out – they were turkeys, and when his ship eventually docked in Bristol, he sold them to locals for two pence each.

Or at least this is how Strickland later claimed he had introduced the turkey to England, though it has never been verified. Decades later, Edward VI granted him permission to include the bird in his family crest – the first ever depiction in the Western world.

As it happens, recently further evidence for this story emerged.