What was long thought to be a copy of the Magna Carta at Harvard Law School in the US is in fact an extremely rare original from among seven surviving versions of the document issued by English King Edward I in 1300, British experts said on Thursday.

The "Great Charter," the first extant expression in writing of the principle that a king and his government are not above the law, originally dates from June 1215, when it was signed by King John. Among other things, it was key to the drawing up of the US Declaration of Independence and constitution in the late 18th century.

Harvard obtained the document in the 1940s for just $27.50, the equivalent of just over $470 (€420) today, according to a US Department of Labor inflation calculator.

What did the experts say?

Experts from King's College London and the University of East Anglia (UEA) based their conclusion on an analysis of the document's size and its handwriting.

These were consistent with those in the six previously known originals from the slightly amended set released by Edward I in an act known as the Confirmation of the Charters.

"This is a fantastic discovery," said David Carpenter, professor of Medieval History at King's College London.

"Harvard's Magna Carta deserves celebration, not as some mere copy, stained and faded, but as an original of one of the most significant documents in world constitutional history, a cornerstone of freedoms past, present and yet to be won."

The new insights on the document come as Harvard University has been barred from receiving new federal grants by the Trump administration, which many critics see as violating some of the key principles enshrined in the Magna Carta.

Edited by: Wesley Rahn