Clarence's wife Isabel had in 1475 given birth to a son, Edward, later Earl of Warwick.

She died on December 22, 1476, two months after giving birth to a short-lived son named Richard, and they are buried together at Tewkesbury Abbey in Gloucestershire.

Their surviving children, Margaret and Edward, will be cared for by their aunt, Anne Neville, until she dies in 1485, when Edward is ten years old.

Though most historians now believe Isabel's death was a result of either consumption or childbed fever, Clarence is convinced she had been poisoned by one of her ladies-in-waiting, Ankarette Twynyho, whom, as a consequence, he has judicially murdered in April of 1477, by summarily arresting her and bullying a jury at Warwick into convicting her of murder by poisoning.

She is hanged immediately after trial with John Thursby, a fellow defendant.

Clarence's mental state, never stable, deteriorates from this point and leads to his involvement in yet another rebellion against his brother Edward.

The arrest and committal to the Tower of one of Clarence's retainers, an Oxford astronomer named Dr. John Stacey, leads 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 implicates one Thomas Burdett, and one Thomas Blake, a chaplain at Stacey's college.

All three are tried for treason, convicted, and condemned to be drawn to Tyburn and hanged.

Blake is saved at the eleventh hour by a plea for his life from James Goldwell, Bishop of Norwich, but the other two are put to death as ordered.

This is a clear warning to Clarence, which he chooses to ignore.

He appoints Dr. 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 is a very unwise choice, as he is an ex-Lancastrian who has expounded Henry VI's claim to the throne.

Edward summons Clarence to Windsor, severely upbraids him, accuses him of treason, and orders his immediate arrest and confinement.

Clarence is imprisoned in the Tower of London and put on trial for treason against his brother Edward IV.

Clarence is not present—Edward IV himself prosecutes his brother, and demands that Parliament pass a Bill of Attainder against his brother, declaring that he is 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, he is "privately executed" at the Tower on February 18, 1478, by tradition in the Bowyer Tower, and soon after the event, the rumor gains ground that he had been drowned in a butt of Malmsey wine.

Shortly afterward, his son Edward Plantagenet is created Earl of Warwick.

Henry VII’s stridently anti-Lancastrian queen, Elizabeth of York, with her sister and John de la Pole, has had young Lambert Simnel trained to impersonate Edward, Earl of Warwick, a Yorkist incarcerated in the Tower of London.

The conspirators in 1486 had arranged to introduce Simnel to Yorkist Ireland, where he had mustered strong support and was crowned king.

The following year, Simnel returns to England with several thousand mercenaries commanded by Pole and paid by Burgundy.

Henry’s troops defeat and kill Pole and capture Simnel, who receives a royal pardon. (Simnel, according to legend, becomes a scullion in the royal kitchen.)

Warbeck, after eighteen months at court, had tried to escape, but had been quickly recaptured.

He has since been then held in the Tower, initially in solitary confinement, and later alongside Edward, Earl of Warwick; in 1499, the two try to escape.

Captured once again, on November 23, 1499, Warbeck is drawn on a hurdle from the Tower to Tyburn, London, where he reads out a confession and is hanged.

Perkin reportedly resembled Edward IV in appearance, which has led to speculation that he might have been Edward's illegitimate son, or at least had some genuine connection with the York family.

Francis Bacon believed he was one of Edward's many illegitimate children.

It has also been suggested that he was a son of one of Edward's siblings, either Richard III or Margaret of York, Warbeck's first major sponsor.

Some authors, for example Horace Walpole, have even gone as far as to claim that Warbeck actually was Richard, Duke of York, although there is little academic support for this view.

Edward, earl of Warwick, only ten years old, had been kept as prisoner in the Tower of London by Henry VII after the death of King Richard III in 1485.

His claim, albeit tarnished, remains a potential threat to Henry, particularly after the appearance of the pretender Lambert Simnel in 1487.

He had been confirmed in 1490 in his title of Earl of Warwick despite his father's attainder (his claim to the earldom of Warwick being through his mother), but he remains a prisoner until 1499, when he becomes involved (willingly or unwillingly) in a plot to escape with Perkin Warbeck.

Warwick had appeared on November 21, 1499, at Westminster for a trial before his peers, presided over by John de Vere, Earl of Oxford

A week later, in a final neutralization of the Yorkist claim to the throne, Warwick is beheaded for treason on Tower Hill.

Henry VII pays for his body and head to be taken to Bisham Abbey in Berkshire for burial.

It is thought at this time that Warwick has been executed in response to pressure from Ferdinand II of Aragon and Isabella I of Castile, whose daughter, Catherine of Aragon, is to marry Henry's heir, Arthur.

Catherine is said to feel very guilty about Warwick's death, and that her trials in later life were punishment for it.

A number of historians have claimed that Warwick had a mental disability.

As Hazel Pierce points out, however, this surmise is based entirely on a statement by the chronicler Edward Hall that Warwick had been kept imprisoned for so long "out of all company of men, and sight of beasts, in so much that he could not discern a goose from a capon."

It seems likely that Hall simply meant that long imprisonment had made Warwick naive and unworldly.

Upon Warwick's death, the House of Plantagenet becomes extinct in the legitimate male line.