George Osborne has discovered he too could be Jewish after a Beth Din ruled his brother did not need to complete a conversion to marry his American fiancée.

The former chancellor of the exchequer was told by Theo Osborne, his youngest brother who works as an investment manager, that a rabbinical court had ruled he was Jewish after uncovering documents that proved his grandmother had been member of a synagogue in Budapest.

The younger Mr Osborne, 33, was going through a conversion to marry Justine Fisher in an Orthodox ceremony, but discovered the paperwork including Hungarian birth certificates that proved the maternal family’s Jewish origins.

The couple were married in what the Daily Telegraph said was an Orthodox ceremony last weekend in the Wormsley estate in Buckinghamshire.

“The whole family was thrilled to be at my brother Theo and Justine’s wedding on Sunday and to have enjoyed all the tradition and splendour and energy of a great Jewish wedding,” the ex-chancellor told the newspaper.

The Osbornes’ grandmother, born Clarisse Feher but known to the family as Klara, died in 2004 at the age of 90 but did not tell her grandchildren they were technically Jewish.

A family friend was quoted by the newspaper as saying: “It wasn’t something she ever talked about.

“She never discussed her Jewish roots. She had never suggested she was Jewish. She hadn’t come to Britain as a refugee from the Nazis or anything like that.

“She came in the 1930s to study at art college and then stayed. Her parents came from Budapest after the war and settled in London.”