aerial photograph of Canterbury Castle England UK. Canterbury Castle is a Normal Castle built shortly after the Norman Conquest. Originally a Motte & Bailey Castle, the great stone Keep was added by Henry I in the 12th Century.By the 14th century the castle was in ruins, however the Keep continued to be used as a Gaol, particularly during the reign and religious persecutions of Bloody Mary (1553-1558).In the 19th century the building was used by the local gas works however it was Scheduled in 1915 and eventually purchased by Canterbury City Council in 1928.