English: Cromwell's Castle and Hangman Island from Bryher Looking north east from Bryher across New Grimsby Sound towards Tresco. Various origins for the name of Hangman Island have been suggested, from the more prosaic that it is simply a distortion of the old Cornish "An Main" meaning the island (a little unlikely given that the Scilly Isles comprise nearly sixty islands?) to the more dramatic that it was used as a gallows site during the Civil War. Cromwell's castle was built in 1651 to protect the entrance to New Grimsby Sound from potential Dutch invasion. It replaced King Charles Castle, built a century earlier higher up the hill, but which proved ineffective as its guns could not depress sufficiently