The original copy of the Magna Carta was written in Hebrew, newly discovered evidence has shown.

Clerks at King John's court charged with compiling the "Great Document" 800 years ago turned for help to a Jewish lawyer, known as David of Cheapside, it is now believed.

Esther Smythe, professor of historical documentation at University College London, said recently unearthed papers showed that David was brought in to draft the complex legal clauses that had proved beyond the skill of John's scribes.

Ms Smythe said documents dating back to the 13th century had been uncovered in the archive at Taschen Castle, in Lincolnshire, which contained an account by a clerk called Gerald Haman.

Gerald describes how courtiers sought out David and begged him to draw up the charter. He writes that the first copy delivered to the court was in English but with an original in Hebrew, entitled Ha megila Hagdola, attached.

Among Magna Carta's 63 clauses is the right of every person to fair trial and the principle that even the king is subject to the law. "It's very exciting," said Ms Smythe. "It seems the charter guaranteeing many of the rights we now take for granted was Jewish in origin."

Medieval historian Hugo Mord-Kay, said that the evidence suggested that David had taken the opportunity to add clauses, including one allowing Jews to own castles and another lifting taxes on all schmaltz products. These were excised from the final document.