A rare copy of the Magna Carta which had gone unnoticed for generations has been unearthed by researchers.

The 14th-century copy which dates to the reign of Edward I is one of just a handful of rolls reciting clauses from the famous charter.

It was found by researchers preparing for the charter’s 800th anniversary on Monday and they believe its existence may until now have been completely unknown to historians.

Although such documents – used to circulate parts of the Magna Carta across the country –  were once commonplace, very few survived because in medieval times people would use the parchment they were made from for lighting fires or as animal feed, archivists said.

While it had been preserved in archives at St John’s College, University of Cambridge, it appears to have been completely overlooked.

The college was recently contacted by Nicholas Vincent, from the University of East Anglia, who was researching the Magna Carta.

He realised the item was in fact an early example of a statute roll. Only about a dozen of these are known to exist today.

Tracy Deakin, archivist at St John’s College, said it was not uncommon for long-forgotten historical documents to resurface.

She said: “This sort of discovery is a lot more typical than people might think.

“A couple of generations back, archivists did a very different type of job and would not have been able to command the same kind of accessible detail about everything in their archive in the way that we can now.”

The Magna Carta was agreed by King John at Runnymede on June 15 1215. It promised improved rights, including protection from illegal imprisonment and access to justice.

The document can be viewed online at www.joh.cam.ac.uk/archives