Castle Cornet, which now forms part of the southern breakwater to St. Peter Port harbour, Guernsey, was originally sited on the tidal island of Little Russel and took fully fifty years to complete. Work commenced in 1206, following the division of the Duchy of Normandy in 1204, and the fortress thereafter remained basically unaltered until 1545-48 when it was extensively remodelled to reflect the changing realities of War caused by the introduction of cannon and gunpowder. For many years the residence of the Governor of Guernsey, the castle was eventually joined to Guernsey itself when the island of Little Russel was incorporated into the new southern breakwater completed after the Napoleonic Wars.
In this interesting topographical work, Monamy shows the castle marooned offshore by the high tide. The saluting warship crossing the open water between the citadel and the nearby harbour (out of view on the left) merely serves to emphasise the castle's strategic position when it was unassailable except from the sea.