By Mario Cacciottolo
Here's a question with pub quiz potential - which document did Abraham Lincoln refer to as "the Magna Carta of human liberty"?
The answer is the Declaration of Independence, and the former American president's reference to the 13th Century English legal document speaks volumes about its continuing resonance through the ages.
The latest chapter in the history of the Magna Carta is the sale of one example of it, sealed by King Edward I and dating from 1297, which has been sold at Sotheby's in New York for £10.6m ($21.3m).
To clear up any confusion, bear in mind that the Magna Carta - meaning Great Charter - is not just one document. It is a number of them, from different dates, all referred to under the same collective name.
It came into being as the result of a dispute between King John, English barons and the political community of the kingdom, and went some way towards limiting the authority of the king.
The first was sealed in 1215, and not signed as is often thought, by King John at Runnymede. The final one was issued in 1300.
This has led to 17 surviving versions from the 13th Century, including the one sold at Sotheby's.
Hugh Doherty is an expert in historical charters, who works as a researcher at the University of Oxford.
He was asked to help research the Magna Carta and that painstaking work was then used by Professor Nicholas Vincent, of the University of East Anglia, who actually wrote most of the catalogue for Sotheby's auction.
Despite all the centuries of scholarly research, however, it is still not clear who even drafted this charter in the first place.
"Some scholars believe it was the Archbishop of Canterbury, Stephen Langton, but others think it was interplay between a group of northern barons, the Archbishop of Canterbury and southern landowners," said Hugh.
"And of course there would have been those who had the King's interests at heart involved in the negotiation as well."
Whatever its origins, the charter guaranteed basic freedoms and property rights to those considered "free men".
This factor is one of its more remarkable elements, according to Hugh.
King John actually sealed the Magna Carta, rather than signing it
"It is remarkably detailed about issues regarding laymen. It has minutia detail of immediate relevance to the great men of the realm, knights of the shire and free men.
"That last term has been long debated as to its meaning, but broadly it's all those who hold their land freely."
The Magna Carta has had a tempestuous and hotly-debated life, being re-negotiated on four occasions within the first decade of its existence, as both the King and England's earls, bishops and barons all attempted to re-define its terms.
For example, in 1217 an important supplement to the Magna Carta was issued, called the Charter of the Forest, which limited the authority of the king to mulch - or financially squeeze - money out of people over lands designated as being part of the king's forest.
This provided economic protection for the kingdom's poorer subjects, at a time when the forests were the most important potential source of fuel for cooking, heating and industry.
Each time a Magna Carta was re-issued because of a change, an amendment or when a point was qualified, a number of authentic copies by the English Chancery were sent out to each county in the land.
These copies, known as engrossments, could number around 40 or even more, and were sent to county courts among other destinations.
"It's not as though there's just one engrossment in the King's archive. It's a document that has such political relevance and resonance for the political community of the shires," Hugh said.
But in the 13th and 14th centuries, the Magna Carta lost its political importance, as it was overtaken by new documents of law that were drawn up.
Then in the 17th Century the Magna Carta made a comeback, being used against the Stuart monarchy.
"Regardless of its detail it becomes a key document in anti-Stuart rhetoric.
"Charles I, for example, tries to renew the collection of fines for using the king's forest - abolished by the Charter of the Forest - much to Parliament's horror."
Hugh describes the Magna Carta as having a "remarkable afterlife". An example of this is the current political argument taking place in Bolivia over a new suggested constitution for the government, called the Carta Magna.
The original set of rulings still have some resonance in modern-day English law, as they contain the principle of Habeas Corpus, which protects people against unlawful imprisonment.
Also, the right of trial by jury can be traced back to the Magna Carta.
And it is a document that was much studied and revered in the United States several centuries ago, as that nation fought for its independence from Britain.
"Thomas Jefferson looked to the Magna Carta for a variety of reasons, when he addressed the English governors and the government of George III," said Hugh.
Four engrossments of the Magna Carta went on display in Oxford
"Abraham Lincoln also used it in what is known as his 'great debates'. These were key arguments against that really captured the public's imagination in the 1850s."
In early December there was a one-day, one-off display of the four engrossments of the Magna Carta held by the Bodleian Library at the University of Oxford.
Hugh Doherty explained how this event saw 700 people arrive for a viewing, with still more being turned away.
There were, he said, two main questions that the public asked.
"The most common query was whether this is the closest the nation has to a written constitution.
"The answer is no, it's too specific. It's not like people today are still arguing over whether the king's officials can take horses, carts and manpower for his use."
The second most common question was, apparently, why there are holes in the documents. Not political ones, but actual physical gaps.
Hugh can answer that query in just one word.