Nguồn: https://en.wikipedia.org/wiki/George_Plantagenet,_Duke_of_Clarence#Death

George Plantagenet, Duke of Clarence (21 October 1449 – 18 February 1478), was the sixth child and third surviving son of Richard Plantagenet, 3rd Duke of York, and Cecily Neville, and the brother of English kings Edward IV and Richard III. He played an important role in the dynastic struggle between rival factions of the Plantagenets now known as the Wars of the Roses.

Though a member of the House of York, he switched sides to support the House of Lancaster, before reverting back to the Yorkists. He was later convicted of treason against his elder brother, Edward IV, and executed, allegedly by drowning in malmsey wine. He appears as a character in William Shakespeare's plays Henry VI, Part 3 and Richard III, in which his death is attributed to the machinations of Richard.

Death

Though most historians now believe Isabel's death was a result of either consumption or childbed fever, Clarence was convinced she had been poisoned by one of her ladies-in-waiting, Ankarette Twynyho, whom, as a consequence, he had judicially murdered in April 1477, by summarily arresting her and bullying a jury at Warwick into convicting her of murder by poisoning. She was hanged immediately after trial with John Thursby, a fellow defendant. She was posthumously pardoned in 1478 by King Edward. Clarence's mental state, never stable, deteriorated from that point and led to his involvement in yet another rebellion against his brother Edward.

In 1477 Clarence was again a suitor for the hand of Mary, who had just become duchess of Burgundy. Edward objected to the match, and Clarence left the court.

The arrest and committal to the Tower of London of one of Clarence's retainers, an Oxford astronomer named John Stacey, led to his confession under torture that he had "imagined and compassed" the death of the king, and used the black arts to accomplish this. He implicated one Thomas Burdett, and one Thomas Blake, a chaplain at Stacey's college (Merton College, Oxford). All three were tried for treason, convicted, and condemned to be drawn to Tyburn and hanged. Blake was saved at the eleventh hour by a plea for his life from James Goldwell, Bishop of Norwich, but the other two were put to death as ordered.

This was a clear warning to Clarence, which he chose to ignore. He appointed John Goddard to burst into Parliament and regale the House with Burdett and Stacey's declarations of innocence that they had made before their deaths. Goddard was a very unwise choice, as he was an ex-Lancastrian who had expounded Henry VI's claim to the throne. Edward summoned Clarence to Windsor, severely upbraided him, accused him of treason, and ordered his immediate arrest and confinement.

Clarence was imprisoned in the Tower of London and put on trial for treason against his brother Edward IV. Clarence was not present – Edward himself prosecuted his brother, and demanded that Parliament pass a bill of attainder against his brother, declaring that he was guilty of "unnatural, loathly treasons" which were aggravated by the fact that Clarence was his brother, who, if anyone did, owed him loyalty and love. Following his conviction and attainder, he was "privately executed" at the Tower on 18 February 1478, by tradition in the Bowyer Tower, and soon after the event, a rumour spread that he had been drowned in a butt of Malmsey wine.

A reason for Edward to have his brother executed may have been that George had "threatened to question the legality of the royal marriage" and he may have discovered from Bishop Robert Stillington of Bath and Wells that George "had probably let slip the secret of the precontract" for Edward's marriage with Lady Eleanor Talbot, although others dispute this.