HMS Ferret was a shore establishment and naval base of the Royal Navy during the Second World War, located in Derry. It was given a ship's name as a stone frigate.
Wikipedia https://en.wikipedia.org/wiki/HMS_Ferret_(shore_establishment_1940)
Address BT47 6, United Kingdom
Coordinates 55°2'15.757" N -7°16'10.15" E
