An original edition of the Magna Carta potentially worth up to £10m has been found in a Kent council’s archives.

Discovery of a version of the document that established the principle rule of law in 1215 was made in the files of the history department of Kent County Council by council community history officer Dr Mark Bateson.

An original Charter of the Forest issued in 1271 was also uncovered in Maidstone, with both documents under the ownership of Sandwich Town Council.

There is thought to be only one other such pair of these historic documents in the world, with the other held in Oriel College, Oxford.

The Sandwich Magna Carta parchment was found filed in a Victorian scrapbook and is thought to be an original from the version issued by Edward I in 1300.

The discovery by Bateson in late December came just months ahead of the 800th anniversary of King John’s concession. The British Library marked the occasion by exhibiting four 1215 editions of the Magna Carta.

Professor Nicholas Vincent of the University of East Anglia who authenticated the document said it was ‘a fantastic piece of news for Sandwich, which puts it in a small category of towns and institutions that own a 1300 issue’.

Mayor of Sandwich, Cllr Paul Graeme, said: ‘On behalf of Sandwich Town Council, I would like to say that we are absolutely delighted to discover that an original Magna Carta and original Charter of the Forest, previously unknown, are in our ownership.

‘To own one of these documents, let alone both, is an immense privilege given their international importance.’