Edward V, King of England - New evidence uncovered in Princes in Tower mystery. Julia Bryson BBC News, Yorkshire

The will of wealthy London widow Margaret Capel was written 33 years after the princes disappeared.

Mrs Capel was the sister-in-law of Sir James Tyrell, who worked for Richard III and was previously named and accused in historical documents of ordering the murder of the two princes.

Prof Thornton's findings feature in the documentary Princes in the Tower: A damning discovery, which features actor and keen historian Jason Watkins and Tracy Borman, an historian and chief curator of Historic Royal Palaces.

It will be broadcast on Channel 5 at 21:00 GMT on 3 December.

In Mrs Capel's will, the chain was left to her son - but it is not known how it came to her possession.

Documentary makers said it was a royal chain of office, which would have been irreplaceable, and forever linked with its owner, as well as being priceless.

They added Sir James' alleged involvement in the disappearance of the princes was first reported by Sir Thomas More, who claimed he had hired two men to carry out the killing.

Prof Thornton said: "The identification of the chain is significant as powerful men of that time wore collars or chains made out of precious metals as expressions of their identities.

"These chains would have carried symbols or badges of their associations and loyalties and of who they were, so this is a very personal possession of the King, clearly identified as his and it is in the hands of Margaret Capel."

He added: "There are various possible reasons for the chain passing into the hands of the Capel family.

"Some are neutral or benign, perhaps part of a process of dispersing the goods of the princes once their status had changed.

"But the connection with Sir James Tyrell adds to the probability that the two boys had died in the way that has traditionally been described."

Ms Borman said: "The fate of the princes in the tower is one of the most intriguing mysteries in the long history of this iconic fortress and palace.

"It continues to fascinate visitors today, more than 500 years after the princes disappeared."

It comes just weeks after new technology recreated the voice of Richard III - giving him a Yorkshire accent.

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Richard III, King of England

Richard of Shrewsbury, 1st Duke of York

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