The overwhelmingly important fact about the trial and later execution of Charles I was that Charles was tried as King of England. He was named as such in the indictment and finally in the death warrent. This was quite deliberate on the part of the parliamentarians. They wished to establish their collective superiority over him. Understandably, Charles refused to recognise any such right. When the Judge reminded him that he was before a Court, Charles replied that he saw that he was before "a Power". He simply refused to recognise the validity of the Court. This is the difference between the 'executions' of Louis XVI and Nicholas II. Louis had been deposed and Nicholas had abdicated before their deaths.
While taking limited action against the regicides, both living and dead - Cromwell, for example, dead since 1658, was disinterred from his tomb in Westminster Abbey and the corpse hanged at Tyburn - Charles II was not especially vengeful. Cromwell's daughters, for example, were welcomed at his Court. Nevertheless, he was careful to date the beginning of his reign from 1649, the date of his father's death, and not from 1660, the date of his restoration. This is reflected in al the Statutes passed by Parliament until the King's death in 1685. Furthermore, none of the peerages granted by Cromwell were recognised as legal by the Restoration Government and this extended to lesser offices also. Samuel Pepys, on being appointed Clerk of The Works at the Admiralty, had to make private arrangements with the office-holder under Charles I who suddenly turned up and demanded compenstion. Therefore, the essential illegality of Cromwell's regime was recognised while some of his legislation was quietly allowed to remain on the Statute Books or was equally quietly confirmed after 1660.
The precise whereabouts of Charles I's coffin at Windsor remained uncertain until it was found in Henry VIII's vault in the reign of George IV. Then the body, which had been embalmed in 1649, was found to be in a very remarkable state of preservation. The story about one of his bones being removed and made into a salt cellar is perfectly true. Queen Victoria, an admirer of the Stuarts, was not amused and ordered its reburial. The same was true of a bone fragment which had apparently flown over the heads of the soldiers on the day of the execution and which had been treasured ever since by the descendants of the woman who had retrieved it.