Cromwell suffered from malaria and from "stone", a common term for urinary/kidney infections. Yet, he was in generally-good health. He was struck by a sudden bout of 'malaria', followed directly by an attack of urinary/kidney symptoms. Although weakened, he was optimistic about the future, as were his attendants. A Venetian diplomat, also a physician, was visiting at the time and tracked Cromwell's final illness. It was his opinion that The Lord Protector's personal physicians were mismanaging his health; leading to a rapid decline and death from malaria on September 3, 1658.
On January 30, 1661, Cromwell's body was exhumed from Westminster Abbey, and was subjected to the ritual of a posthumous execution - He was hanged, drawn and quartered. At the end, his body was thrown into a pit. His severed head was displayed on a pole outside Westminster Abbey until 1685. Since then, it changed hands several times, before eventually being buried in the grounds of Sidney Sussex College, Cambridge, in 1960.
In a related note, it was also on this date in 1649 that Charles I of England was beheaded. Charles refused to enter a plea during his trial, claiming that no court had jurisdiction over a monarch. He believed that his own authority to rule had been given to him by God when he was crowned and anointed, and that the power wielded by those trying him was simply that which grew out of a barrel of gunpowder. The court was proposing that no man is above the law. Over a period of a week, when Charles was asked to plead three times, he refused. It was then normal practice to take a refusal to plead as pro confesso: an admission of guilt, which meant that the prosecution could not call witnesses to its case. Fifty-nine of the Commissioners signed Charles's death warrant, on 29 January 1649. After the ruling, he was led from St. James's Palace, where he was confined, to the Palace of Whitehall, where an execution scaffold had been erected in front of the Banqueting House.
It was common practice for the head of a traitor to be held up and exhibited to the crowd with the words "Behold the head of a traitor!"; although Charles' head was exhibited, the words were not used. It might be, because William Hewlett, the inexperienced stand-by, did not know to do so. In an unprecedented gesture, Oliver Cromwell, allowed the King's head to be sewn back on his body so the family could pay its respects. Charles was buried in private and at night on 7 February 1649, in the Henry VIII vault inside St. George's Chapel in Windsor Castle.