Protected UK-NATO anti-submarine exercise By ANI - May 14, 2023 0 221 HMS Northumberland at sea on operations. HMS Northumberland is a Royal Navy Type 23 frigate, based in Plymouth. The frigate specialises in hunting submarines and currently has a Royal Navy Merlin embarked for the frigate’s current taskings. Source: Royal Navy The Royal Navy and NATO have completed their largest anti-submarine warfare exercise in the North Atlantic, designed to enhance allies’ ability to track and destroy threats lurking beneath the surface, Naval Technology reports. Please Login to view this content. (Not a member? Join Today!)