A hammer-wielding man has been arrested after an attempted smash and grab of a Magna Carta from its display at Salisbury Cathedral.
Alarms went off when the would-be thief tried to break through the glass box which protects the charter on Thursday.
The suspect was held on suspicion of attempted theft of the document - claimed to be the best preserved of four original Magna Cartas.
It was not damaged and nobody was injured, police said.
The man was wrestled to the ground by staff when he attempted to flee after the attempted raid at 16:45 BST, the Dean of Salisbury said.
The Very Reverend Nick Papadopoulos said: "There were people around so the cry went up, it was pretty thick glass so it hadn't yielded easily despite having a hammer hit it.
"It was a great shock but everyone responded magnificently, both our staff and volunteers and members of the public.
"They raised a cry and he did not get away."
The drama unfolded just before Evensong near to closing time at the visitor centre.
Dean Papadopoulos added: "He had been carrying a hammer so our guys were very courageous.
"They were able to restrain him and they held him for 12 minutes."
A silent alarm was activated which alerted staff to the disturbance, he added.
A 45-year-old man is being held on suspicion of attempted theft, criminal damage and possession of an offensive weapon.
He has been taken to Melksham police station where he is being questioned.
Magna Carta is a charter of rights agreed by King John in 1215. It is considered one of Britain's most influential legal manuscripts.
Several versions were sent around the country "as evidence of the King's decision", according to Salisbury Cathedral's website.
Only four original copies survive today, and the cathedral is home to what is claimed to be "the most beautiful".
The charter was put on display at the cathedral three years ago as part of an exhibition funded by the Heritage Lottery Fund.
The charter has been removed for safe-keeping while the case is refurbished, Dean Papadopoulos said.
A facsimile copy of the charter will be displayed, and the visitor centre will re-open as soon as possible.
What is Magna Carta?
Magna Carta outlined basic rights with the principle that no one was above the law, including the king.
It charted the right to a fair trial, and limits on taxation without representation.
It inspired a number of other documents, including the US Constitution and the Universal Declaration of Human Rights.
Only three clauses are still valid - the one guaranteeing the liberties of the English Church; the clause confirming the privileges of the city of London and other towns; and the clause that states that no free man shall be imprisoned without the lawful judgement of his equals.
The British Library has two copies of the 1215 Magna Carta.
Source: The British Library
The historical document is encased in two glass layers, Dean Papadopoulos added.
"The layer that is closest to the document itself was completely untouched by the individual concerned, but his hammer did do some damager to the initial glass screen."
Two copies of the Magna Carta that date from 1215 are held by the British Library and go on regular display there.
The Salisbury copy went on display in 2015 in the 13th Century Chapter House at the cathedral.