David Cameron has spoken of the need to reform UK human rights to "safeguard" the Magna Carta's legacy as the historic document's influence over the past 800 years was celebrated.
The Prime Minister's words came at a major international event, attended by the Queen and an audience of thousands, marking the groundbreaking accord's role in helping to define concepts such as the rule of law and equal rights for all.
On the site at Runnymede where King John, on June 15 1215, accepted the historic document that limited the power of the Crown, Mr Cameron said it remains "sewn into the fabric of our nation, so deep we barely even question it" but complained that the notion of human rights in Britain has been "distorted and devalued".
Among those at the celebration were senior members of the Royal Family, the Archbishop of Canterbury and Lord Dyson, Master of the Rolls and chairman of the Magna Carta Trust.
Lord Dyson said in a speech to guests: "Magna Carta has had its ups and downs. But it was a hugely significant step on a journey which led to the building of a society where everyone has equal rights and nobody is above the law."
The Conservative Government has controversial plans to scrap the Human Rights Act and assert the role of the UK's Supreme Court over the European Court of Justice in Strasbourg - leaving open the option of withdrawing from the European Convention of Human Rights if reforms are blocked.
Mr Cameron said in his speech: "It falls to us in this generation to restore the reputation of those rights - and their critical underpinning of our legal system.
"It is our duty to safeguard the legacy, the idea, the momentous achievement of those barons. And there couldn't be a better time to reaffirm that commitment than on an anniversary like this.
"So on this historic day, let's pledge to keep those principles alight."
Although just three of its clauses remain law in the UK, Magna Carta set a precedent which saw it influence later works domestically and abroad, including the US Constitution and the Bill of Rights, and the post-Second World War UN Universal Declaration of Human Rights.
Mr Cameron said Magna Carta had been "revolutionary - altering forever the balance of power between the governed and the government".
Down the years it had inspired the fighters in the English Civil War, the Chartists, the Suffragettes, the founders of the first American states, Gandhi, Nelson Mandela and "anyone challenging injustice or checking arbitrary power", he added.
He said: "Magna Carta takes on further relevance today. For centuries, it has been quoted to help promote human rights and alleviate suffering all around the world.
"But here in Britain, ironically - the place where those ideas were first set out - the good name of 'human rights' has sometimes become distorted and devalued."
Though more later versions remain, just four known copies of the original Magna Carta (Great Charter) exist today, from an estimated 13 that were made.
Two are held by the British Library, with Salisbury Cathedral and Lincoln Cathedral holding the others. They are written in Latin on sheepskin.
Urging everyone in Britain to take pride in Magna Carta, Mr Cameron went on to say: "Its remaining copies may be faded, but its principles shine as brightly as ever in every courtroom and every classroom from palace to Parliament to parish church.
"Liberty, justice, democracy, the rule of law - we hold these things dear and we should hold them even dearer for the fact that they took shape right here, on the banks of the Thames.
"So on this historic day, let's pledge to keep those principles alight. Let's keep Magna Carta alive.
"Because as those barons showed, all those years ago, what we do today will shape the world for many, many years to come."