What became known as a Council of State was set-up instead of the monarchy and Oliver Cromwell was its first chairman. 
When Charles II returned to become king of England in 1660, those men who had signed his father’s death warrant (and were still alive) were tried as regicides (the murderer of a king) and executed. Anyone associated with the execution of Charles was put on trial. The only people to escape were the executioners as no-one knew who they were as they wore masks during the execution.