Actually, Cromwell wasn't "unseated": he died of natural causes. It was Cromwell who unseated Charles I, and then beheaded him. I'm not sure if Charles' head was displayed on a stake afterwards, although it was a common practice.
Some years after Cromwell's death, when the monarchy was restored, the Royalists dug up Cromwell's skeleton and symbolically "hanged" him for regicide.
Thanks for the history refresher, I must be blurring Cromwell's coming and going stories, coupled with a mental image from some novel of Cromwell's skull on a pike high over London. Certainly a wild time in British history, one I'd not choose to see repeated here. I guess the moral of that story is that the pendulum does swing, doesn't it?