A court has sentenced a man to four years in prison for attempting to steal a copy of the Magna Carta, a 13th century document that cemented a key step on Britain's path to its modern parliamentary democracy.
Salisbury Crown Court in southern England convicted Mark Royden of a failed attempt to steal the document from Salisbury Cathedral on October 25, 2018 by hammering security glass and setting off a fire alarm as a distraction.
Royden, 47, told police he had doubted the authenticity of the document, which the cathedral says is one of just four copies dating back to the signing of the Magna Carta.
Prosecutors said he "carefully planned his route to avoid detection" but failed to break the security glass.
Visitors and staff detained Royden outside the building after he had caused damage costing more than 14,000 pounds ($A25,400) while attempting to steal the document.
"Had he succeeded in taking it, Royden would have deprived the nation of what's said to be the most beautiful surviving copy from 1215," Rob Welling of the Crown Prosecution Service said following Royden's conviction.
King John of England was forced to sign the Magna Carta in 1215 to halt a civil war with powerful barons who wanted greater control of lands and taxes.
It was the first written document to limit the exercise of royal authority, granting all "free men" - about 10 per cent of England's population at the time - the right to justice and a fair trial.
Salisbury Cathedral calls it "a symbol of justice, fairness and human rights".
Australian Associated Press