Expert says discovery of 1300 edition of historic document raises hopes that there are more than the 24 copies currently known about in existence

An edition of the Magna Carta which could be worth up to £10m has been found after it lay forgotten in a council’s archives.

The discovery of the version of the historical parchment which established the principle of the rule of law, in the files of the history department of Kent county council, has been described as an important historical find by an expert.

The document was found in the archives kept in Maidstone but belonging to the town of Sandwich.

Speaking from Paris, Professor Nicholas Vincent, of the University of East Anglia, who authenticated the document, said: “It is a fantastic discovery which comes in the week that the four other known versions were brought together at the Houses of Parliament.

“It is a fantastic piece of news for Sandwich which puts it in a small category of towns and institutions that own a 1300 issue.”

Vincent said the fact Sandwich had its own Magna Carta gives backing to the theory that it was issued more widely than previously thought to at least 50 cathedral towns and ports.

And he added the discovery gives him hope that further copies will also turn up.

There are only 24 editions of the Magna Carta in known existence around the world.

Vincent said: “It must have been much more widely distributed than previously thought because if Sandwich had one ... the chances are it went out to a lot of other towns.

“And it is very likely that there are one or two out there somewhere that no one has spotted yet.”

Vincent, who specialises in medieval history, said the value of the Sandwich edition could be up to £10m, but it was ripped with about a third missing.

He said: “This would be an upper value as it has, like the town of Sandwich, suffered over time from French invasions and the like.”

The discovery was made by archivist Dr Mark Bateson at the end of December just before the 800th anniversary year celebrations of King John’s concession.

The Sandwich Magna Carta was found when Vincent asked Bateson to look up a copy of the town’s original Charter of the Forest.

It was found next to the charter in a Victorian scrapbook and its high value comes from the fact it also comprises the Forest Charter. There is only one other such pair in the world, owned by Oriel College, Oxford.

It is understood that Sandwich does not intend to sell its Magna Carta but instead is hoping to benefit from its potential as a tourist attraction.

Paul Graeme, mayor of Sandwich town council, 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.”

The four known 1215 editions are from Salisbury Cathedral, Lincoln Cathedral and two held at the British Library.

They were brought together for a one-day exhibition at Parliament for a crowd of 2,015 chosen by a public ballot.

Speaking of the exhibition, the Lord Speaker, Baroness D’Souza, said: “Magna Carta established the principle of the rule of law and equality before the law; for 800 years we have been influenced by its contents and it remains one of the most important political documents in the world, with countries such as the United States, Australia, New Zealand and Canada tracing constitutional influences back to Magna Carta.”

The parchment, which was issued by Edward I in 1300, is the final version of Magna Carta and three of its clauses remain on the statute books today.

These include the defence of the church, the protection of the City of London and the right to trial by jury.

The first Magna Carta was drafted by the Archbishop of Canterbury and agreed by King John on 15 June 1215 to make peace with a group of rebel barons. It was reissued and reaffirmed on many occasions in subsequent years.