Above. An early 20th C postcard showing Castle Cornet. The castle has a long history being first built on this site in the 13th C. With the outbreak of the English Civil War in 1642, Castle Cornet, under the command of Governor Peter Osborne, remained loyal to the King. Guernsey supported the Parliamentarians and the castle was under siege for nearly nine years. Although occasionally supplied by ships from Royalist Jersey, the garrison suffered many hardships during the siege. Following the Restoration of the Monarchy John Lambert spent 9 years imprisoned there.