Two winters ago Nicholas Zhang, then 16, set off from Hong Kong on a 12-hour train journey. His destination: the city of Kaifeng, on the Yellow River, in the central-eastern province of Henan, some 1,000 miles away.

In the 11th century, it was the capital of the Song Dynasty. But while he is a keen student of history, its imperial past was not what had attracted him. He was going in order to find out more about one of the world’s more unusual Jewish communities.

It was founded more than a thousand years ago by Jewish traders from Persia and Babylon travelling along the Silk Road. At its heyday, the community was thought to have numbered 5,000. They were known variously as the “sect who pluck the sinew” — a reference to the removal of the sciatic nerve from kosher meat in commemoration of Jacob’s tussle with the angel — or “blue-capped Muslims”.

Over time, they intermarried so they became indistinguishable in appearance from the indigenous Han Chinese. Their names were sinified, Leviticus becoming Li, Shimon, Shi. In contrast to the kind of restrictions that constrained Jews in Christian Europe, they were free to take positions in the Chinese civil service and many did.

But their ability to maintain their religious traditions weakened. The last rabbi died more than 200 years ago, one of the floods that perennially afflict the city destroyed their last synagogue in the middle of the 19th century.

Now there remain around 1,000 people who identify as descendants of Kaifeng Jewry. While Judaism is not one of China’s five recognised religions, they have retained a sense of their cultural heritage and family lineage. Over the past decade or so, some 20 have made aliyah to Israel through the assistance of the “lost tribes” organisation, Shavei Israel.

In Kaifeng, Nicholas met Esther Guo, who runs a Jewish museum in her home, and was struck by some of the artefacts he was shown.

“Imagine going to a place in the middle of China and finding a fully handwritten Torah in Chinese,” he said. It was written as a book, like a Chumash.

A quotation from Isaiah was displayed on a banner in Hebrew and Chinese , “My house shall be called a House of Prayer for all peoples”.

For Nicholas, who is currently studying for the International Baccalaureate at St Clare’s in Oxford, interest goes beyond intellectual curiosity. “I want to play a role in preserving their culture and identity,” he said.

When he returned, not only did he create a website, chinesejews, and recruited some of his fellow students as “ambassadors” to spread the word, but remarkably, he has written a book, Jews in China: A History of Struggle. He also devoted his IB extended essay to the history of Kaifeng Jewry.

He was motivated to do his book because he wanted to produce something more accessible than the scholarly literature on the topic he found in libraries. “The average Chinese or Jewish person doesn’t read academic articles or books,” he said.

While he has no Jewish ancestry himself, his family story has a Jewish link. “My great-grandmother was from quite a wealthy family in China. She left for a holiday in 1949 but then the Communist Party took over and she couldn’t go back to China.”

She was able to find refuge in the USA after being given a job in the Concord Hotel in the Catskills, which was owned by a Jewish family, the Parkers. Separated from her five children, she was unable to go back to her homeland until some 30 years later.

By then, her children had families of their own. The Parkers agreed to sponsor her eldest child to come to the States and gradually her other children followed. “My mum’s cousin married a Jewish woman so now I have Chinese-Jewish cousins,” he said.

He grew up in Hong Kong, where his mother had moved in the 1990s. At 13, he was sent to study at a traditional English boarding school. “I love history,” he said. “I learned about the Cold War, the First World War, the Second World War and the Holocaust — it seemed almost surreal, I didn’t see how something like that could happen.

“When I was back in Hong Kong, I went to a Yom Hashoah event which was hosted by the Hong Kong Holocaust and Tolerance Centre. It was founded by survivors who came to Hong Kong. The guest speaker was Ronald Leopold, director of the Anne Frank House in Amsterdam and he invited me to visit.”

The story of Kaifeng Jews is a story of co-existence, and telling it, he believes, is a way to counter intolerance. “The confluence of two civilisations produced something special.”

As he wrote on his website, “After centuries of intermarriage and millenniums of assimilation, these children of Abraham and Sarah, sculpted by teachings of Confucius and Lao Tzu, emerged with an identity and culture that is uniquely their own, unseen anywhere in the world.”

Nicholas Zhang will be speaking at the Limmud Festival on December 23. For more about his project, visit the website here.