On Monday, the library announced plans to mark the anniversary by bringing together — for three days only — all the remaining original copies of the charter endorsed by King John in June 1215 to quell an uprising by England's nobles.
"Multiple copies were written up and sent to the bishops and possibly the sheriffs" across England, said Claire Breay, the library's lead curator of medieval manuscripts. "It's four of those that survive."
Two are in the British Library's collection, while one is at Lincoln Cathedral in central England and another resides at Salisbury Cathedral in southwest England.
Early in 2015, the four documents will be scrutinized by researchers — and visited by 1,215 members of the public selected through a competition.
Breay said that seeing the copies side-by-side may give academics new insights into the documents and the scribes who wrote them out in Latin on sheepskin parchment.
Britain plans a year of celebrations in 2015 for the anniversary of the Magna Carta, which became the first building block of its constitution — a constitution made up of a series of laws and conventions, rather than a single document.
The Magna Carta — the Great Charter — was endorsed by King John to resolve an uprising by nobles angered by the monarch's despotic behavior and extortionate taxes.
The four original copies are written records of an oral agreement made between the king and his barons at Runnymede, west of London. The agreement outlined limits on the power of the crown, establishing that the king was subject to the law, rather than above it.
Its most famous passage was interpreted as laying the foundations of trial by jury:
"No free man shall be seized or imprisoned, or stripped of his rights or possessions, or outlawed or exiled, nor will we proceed with force against him, except by the lawful judgment of his equals or by the law of the land."
Breay said it's a historic landmark that almost wasn't.
"It was only valid for less than 10 weeks," she said. "The barons, knowing what King John was like, put in a clause making him say he would not seek to have it annulled. Almost the first thing he did was send someone off to Rome to Pope Innocent III to seek to have it revoked."
The pope did annul it, and England was plunged back into civil war. But King John died the next year, leaving his 9-year-old son on the throne as Henry III. The regent who ruled for young Henry re-issued the Magna Carta.
Although many of its clauses were subsequently ignored, overturned or rewritten, the document is considered the basis of British law and a major influence on subsequent documents, including the U.S. Constitution.
The Magna Carta was re-issued several times in the 13th century and 17 of these later copies survive. Fifteen are in Britain, one is displayed at Australia's parliament and one, dating from 1297, is in the U.S. National Archives.