Archaeologists digging on the site of demolished shops overlapping Oxford’s old Jewish quarter were stunned to find clear evidence that medieval Jews did observe the dietary laws of kashrut.

Dr Julie Dunne, the bio-molecular archaeologist at Bristol University who worked on the 2016 project — whose findings the JC can reveal today — says they were “blown away” by what they discovered in the centuries-old latrine and rubbish tip.

“Normally you would expect a mixture of cow, sheep, goat and pig. Instead we found a massive, I mean massive, amount of chicken and goose bones.” Out of 171 bones recovered from the site, 136 were some kind of poultry. More important still, there was a complete absence of pig bones, hindquarters of cows, shellfish or any other non-kosher food.

More than 2,000 fragments of pottery were also found on the site, enabling Dr Dunne and her colleagues to go even further into the dietary world of medieval Jewry.

Using organic residue analysis, they were able to identify the particular kinds of fat that had been absorbed into ceramic cooking vessels 800 years earlier and then sealed into the pottery through years of constant use (in much the same way as we season a cast-iron frying pan).

“This process allows us to distinguish animal fats from ruminants and non-ruminants, as well as from dairy products,” said Dr Dunne, “and what we found was astonishingly precise.”

The fats in the pots exactly followed the findings from the bones. Not only were there no traces of non-kosher food, there was no evidence of meat and milk ever being used in the same vessels.

These results held only for the area of the site that had been lived in by Jews and only for the period in which Jews lived in medieval England. Beyond the precise boundaries of this area and these dates, from the 8th century to the 18th century, it was a non-stop, non-kosher carnival.

Until now, there has been surprisingly little firm evidence to support the assumption that Jews in medieval England ate kosher.

Thanks to the preservation of Jewish manuscripts, contracts and property deeds by Oxford’s colleges and libraries, documentary information about Oxford’s medieval community is exceptionally rich.

But virtually all physical traces of this once-thriving Jewry have vanished since the 1290 expulsion. In addition, the excavation site in the modern city’s commercial centre had been repeatedly built over in the centuries since. It was a long way from a “pristine site”.

The chance to excavate the site very nearly didn’t happen. Commercial developers had already reached the final stages of gaining planning permission and it was only a last minute appeal by historian Pam Manix and Dr Evie Kemp, members of the Oxford Jewish Heritage Committee, that brought archaeologists the time they needed.

“Oxford Preservation Trust got in touch just days before the last meeting,” recalled Ms Manix, “and asked if I’d attend and raise an objection.”

Ms Manix needed no persuasion. An expert on medieval Jewish Oxford, she’d previously helped to identify the first Jewish cemetery in Oxford (now under Magdalen College) and St George’s Tower in the castle where Jews were imprisoned on coin clipping charges in 1278. Having spent years mapping Jewish property ownership in the 12th and 13th centuries, she knew exactly how significant the site was from a Jewish perspective. “I realised at once this was an amazing opportunity. It was the first time in decades the site had been opened up and it was right on top of a property called Jacob’s Hall, which had belonged to Jacob of Oxford, one of the most important Jews in England.”

Jacob’s Hall was one of five enormous stone mansions belonging to Jewish magnates that once stood on both sides of Great Jewry, now St Aldate’s. Its large underground vaulted chamber may have served as the synagogue until 1228, and the building may also have housed a yeshiva and mikvah. Jacob’s Hall survived until 1644 as a student hostel belonging to Merton College.

Jacob himself was a major property owner and developer in Oxford, who designed and built the first student accommodation in Oxford (now the site of the Story Museum), which he sold in 1267 to Walter de Merton, founder of Merton College. In the last years of his life he held the prestigious post of Keeper of the Queen’s Gold. Not that this stopped the queen from doing Jacob’s widow and sons out of their inheritance when he died in 1277.

Jacob of Oxford’s family was hugely eminent, the Rothschilds of medieval England, tracing their lineage back to Rabbi Simeon the Great of Mainz. His father was the great medieval scholar, Master Moses of London.

After Dr Manix’s intervention, development of the site was halted for four months to allow for proper archaeological excavation. Initial excitement rapidly turned to disappointment when it transpired the only part of Jacob’s Hall to be explored was the backyard, containing just the midden and the latrine – in other words, the rubbish dump and the loo.

What seemed like a dead-end turned out to be a treasure trove. “I was initially crestfallen,” admitted Ms Manix, “but the archaeologists were thrilled. Talking about what the midden might uncover, we realised it could provide really valuable information about the dietary habits of medieval Jews.” None of them anticipated quite how valuable. As Dr Dunne said: “The science, the archaeology, the documents all married together so beautifully.”

Jews in medieval England were in many ways indistinguishable from their non-Jewish neighbours. They lived cheek-by-jowl with Christians, dressed in the same fashions, walked the same streets, shopped and traded in the same markets. Even after 1218 when all Jews in England were ordered to wear a badge of the tablets of the law prominently displayed on their outer garments, many individuals and communities simply paid not to.

What emphatically did distinguish Jews was their religion, and what these findings emphatically prove is that this extended to what they ate and how they prepared and cooked their food. There are only three other examples of evidence that Jews kept kosher, all from continental Europe not England.

This is the first firm evidence that Jews living in England in the 12th and 13th centuries strictly observed Jewish dietary laws, and as Dr Dunne says, “the first time a religious dietary signature has been identified using pottery fragments.”.

Ms Manix, for one, is jubilant. “I thought it was wishful thinking that we were going to find anything this distinctive. The fact that we’ve pulled all this information out of a midden and a latrine is just astonishing.”

But then as the Jewish proverb says, “Better an ounce of luck than a pound of gold.”

Rebecca Abrams is the author of ‘The Jewish Journey: 4000 years in 22 objects’, and co-editor of Jewish Treasures from Oxford Libraries