Only copy of Magna Carta in private hands to be sold in New York

The Magna Carta, which set out the most basic principles of English law, is recognised as one of the most important documents in existence. So rare are the surviving 17 versions of the manuscript, drawn up by King John in 1215, that all but two reside in Britain's most hallowed institutions, including the British Library and Salisbury Cathedral.

But yesterday, in an extraordinary announcement, Sotheby's revealed that the only copy of the Magna Carta in the world to remain in private hands will be auctioned in New York this December. It dates from 1297 – the year the final versions of the charter were ratified – and it is likely to be the only version ever to be sold.

As one of only two versions outside England – the other belongs to Australia – the sale, which even by conservative estimates is expected to fetch £15m, has been hailed as momentous. David Redden, vice-chairman of Sotheby's, said that, as "the most important charter in the world", it had become a worldwide phenomenon. "The document symbolises mankind's eternal quest for freedom," he said. "It is a vessel for everyone's hopes and fears; it tells us how the concept of freedom in law began. If we go back to find the seed from which it all comes back to, the Magna Carta has had a huge impact which resonates today."

Written in Latin by a royal scribe on vellum or animal skin, the Magna Carta, translated as "great charter", was originally created by King John, who reluctantly renounced certain kingly rights, agreeing that his will could be bound by law and vowing to respect specific legal procedures after being put under pressure by his increasingly restive barons.

About 400 versions of the charter were said to have been issued during the 13th century, including those that were re-issued, after a determined campaign from the barons, with changes inserted each time. In 1297 the final version was confirmed, which included the right not to be jailed unlawfully and to trial by jury. Only four versions from this date survive today.

Never having been sold at auction before, the document going under the hammer in New York sat for years in the archives of the Brudenells, one of medieval Britain's most prominent families. It is believed to have come into their possession from ecclesiastical archives after the dissolution of monasteries, and was mistaken for an unimportant 13th-century document by the family before its significance was finally recognised in the 1970s.

Mr Redden said: "Until the Seventies, they thought it was just a medieval charter. It turned out to be 'the' medieval charter of all time." He said it was sold by the Brudenells in 1984 to an American charity, and taken out of the country to be displayed at the National Archives in Washington, a move which would not be permitted today for a national treasure of such immense importance.

Other versions of the document in Britain are at Durham, Salisbury, Hereford and Lincoln cathedrals as well as the four in the British Library, the National Archives, the Corporation of London's record office and Oxford University's Bodleian Library. A copy was sold privately to Australia by Sotheby's in the early 1950s.

Claire Breay, head of medieval and earlier manuscripts at the British Library, said it was of great national and international importance. "Its significance was international because of the impact it had in other countries, and it has echoes in the American Bill of Rights as well as the Universal Declaration of Human Rights. That's why it still gets cited by lawyers and quoted by politicians," she said.

Magna Carta rights

Three clauses of the 1297 version of Magna Carta still remain in legal force in England and Wales, which guarantee the freedom of the English Church, the "ancient liberties" of the city of London and a right to due process.

The charter:

* Bound the king to certain laws regarding the treatment of church officials and nobles.

* Stated that fines should be proportionate to the offence and that people should be tried by their peers, in effect bringing in trial by jury.

* Decided that crown officials, such as sheriffs, may not try a crime in place of a judge.

* It said no one could be tried on their own testimony alone.

* Defined the right of habeas corpus, a legal action or writ through which a person can seek relief from unlawful detention of themselves or another person.

* Said no royal officer could take commodities such as corn, wood or transport without payment or consent in an attempt to eradicate extortion and corruption.

* Bound the king to return any lands confiscated from a felon within a year and a day.

* Set out a list of standard measures and guaranteed the safety and right of entry and exit of foreign merchants.

* Stated the king should appoint royal officers only where they were suitable for the post.