The 800-year-old sheet of parchment that is the Magna Carta is often hailed as one of the world’s most famous historical documents because it laid the foundation for the rights and freedoms on which modern democracy rests.

On Monday, Queen Elizabeth will preside at a celebration at Runnymede Meadow alongside the Thames River, where John, King of England, affixed his seal to the medieval document in 1215. A.E. Dick Howard , a constitutional law professor at the University of Virginia and author of The Road from Runnymede: Magna Carta and Constitutionalism in America, will be there among dignitaries from around the world. “My children would never forgive me if I didn’t go,” he said in an interview from London, where he has been lecturing on the Magna Carta since late May. “It will be like a lawyers’ Woodstock.”

Fittingly, the forecast, as it was for the 1969 rock concert, is for rain.

Ten facts about the Magna Carta that may surprise you:

1. The Magna Carta, written in Latin, was not originally designed as a lofty statement of principles.

The goal was more immediate and practical. It was a peace treaty negotiated by a despotic king to quell a rebellion by 25 barons, who were tired of paying high taxes to fund his reign and forced him to negotiate.

2. Magna Carta was drawn up during the reign of Britain’s worst king.

King John is remembered as Bad King John . His dastardly deeds , too numerous to count, include imprisoning his wife, starving opponents to death, and murdering his nephew. He imposed high taxes and seized property to pay for expensive foreign wars. As if being a tyrant weren’t enough, he was singularly untalented. Despite massive tax hikes to fund his armies, he failed to regain the continental lands he had lost. When British scholar Nicholas Vincent was asked by the Daily Telegraph if Bad King John was deserving of the name, he said, “No. He was much worse than that.”

No other British king since has been named John.

View Images King John signs the Magna Carta in an undated painting. In reality, medieval documents were authenticated by seal, not signature. The document celebrates its 800th anniversary this year. Photograph by Corbis

3. Within 60 days of sealing the document, King John tried to kill it.

Two months after sealing the Magna Carta, the king asked the Pope to nullify it. The Pope complied, and issued a papal bull calling it “illegal, unjust, harmful to royal rights and shameful to the English people.”

4. The Magna Carta might have been forgotten but for King John’s nine-year-old son.

Henry III, King John’s son, assumed the throne after his father died of dysentery in 1216. Within months of his death, in 1217, the Magna Carta was reissued in his name to broker peace with the barons. When Henry turned 18 in 1225, he reissued the definitive Magna Carta himself.

5. The Magna Carta’s most important sections remain in English law today.

Clauses 39 and 40, the most significant and best-known sections of the 3,550-word document, established the rule of law as a fundamental principle: No one, not even the king is above the law. They also ensured basic individual rights and guaranteed justice and the right to a fair trial.

6. The original was also larded with local political deal-making.

An agreement to remove fishing weirs—fish traps—from the Thames and Medway Rivers was written into the text, as well as agreements allowing merchants to travel freely abroad and internally in England except in time of war. Sir Robert Worcester, chairman of the Magna Carta 800th Anniversary Commemoration, said these clauses aimed to placate business-minded barons.

“Removing the weirs was vital to protecting the commercial interest of the City of London,” he said. The document also got a running 13th century start on women’s rights, Worcester said, by prohibiting the remarriage of widows without their consent.

7. Early on, the Magna Carta’s significance was not always recognized.

Even Shakespeare missed it. In his play The Life and Death of King John, Shakespeare mentions neither the Magna Carta nor the balance of power between the king and the noblemen that it established.

8. Later, great world leaders saw its importance as a symbol of liberty.

The Magna Carta’s core principles are fundamental to other historical documents. Thomas Jefferson incorporated its concepts in the Declaration of Independence and the Bill of Rights. Mahatma Gandhi cited it in a farewell letter published when he left South Africa in 1914, noting that it confirms “there should be no legal racial inequality between different subjects of the crown.”

Echoes of the Magna Carta also are contained in the 1948 Universal Declaration of Human Rights and the 1950 European Convention on Human Rights. Nelson Mandela cited the Magna Carta in a famous speech in 1964 while on trial for sabotage—a capital offense in South Africa.

9. Only four copies of the 1215 version remain today.

And there are fewer than two dozen copies of various 13th century versions. Another was discovered earlier this year in a Victorian scrapbook in the town of Sandwich, on the southeast English coast.

The only copy in private hands was bought in the 1980s by Texas billionaire and former presidential candidate Ross Perot , who paid $1.5 million for a 1297 version and loaned it to the National Archives in Washington. In 2007, Perot sold it at Sotheby’s to David Rubenstein, billionaire financier and philanthropist, for $21.3 million. It remains on display at the National Archives.

10. The Magna Carta’s history is so long and complicated even Britain’s prime ministers sometimes get it wrong.

In an appearance on David Letterman in 2013, Prime Minister David Cameron flubbed a quiz about British history, and failed to recall the English translation of Magna Carta. It means “Great Charter.”

“You have found me out. That is bad, I have ended my career on your show tonight,” Cameron told Letterman.

Not quite. In last month’s election, Cameron surprised opponents and won enough votes for a second term in office.