Guernsey, a History for tourism. Culture, People and Environment. Find out about this country’s background information: A British Crown dependency, which, along with the other Channel Islands, remained loyal to the English monarchy when King John lost Normandy to France in 1204, Guernsey has some 1500 years of recorded history having been settled by Britons migrating to Brittany in the 5th century. Part of the medieval Duchy of Normandy, it became inextricably linked to Britain when William the Conqueror gained the crown in 1066 and although occupied by Capetian French and by Aragonese mercenaries during the Hundred Years War, it remained in British hands until the German invasion during WWII. More history and culture information in the book Guernsey History and Travel guide.