Execution
There are other ways a monarch could leave his post in England. Charles I stopped being the king when the Parliamentarians executed him. They defeated the royalist forces during the English Civil War and took his head. He was executed on the accusation of being a tyrant.
Lady Jane Grey
Charles I was not the sole monarch to die by execution. There was also Lady Jane Grey, known as the “Nine Days’ Queen.” She reigned for only 9 days before she was overthrown by her cousin Mary. She was executed within a year. Ouch.