The Maunsell Forts weren't designed to fight in a naval battle. Instead, their purpose was to provide platforms for AA guns in and around the Thames Estuary. These guns would deter German aerial minelaying efforts in the strategically vital sea lanes into the Port of London. They would also spot German air raids using the Thames as a navigation marker on their way to raid London, and attrit their numbers. The forts in the Mersey Estuary were mainly there to deter minelaying efforts, and to aid in the defence of Liverpool from air attack. Both sets of forts were manned from their initial sinking. The Mersey forts never fired a shot in anger - the Germans never tried aerial minelaying in the Mersey. However, the Thames forts were reasonably effective, claiming 22 German aircraft and 30 V1 flying bombs. One of the forts, at Tongue Sands, also claimed a German E-boat (fast torpedo boat) destroyed, though details on this are somewhat sparse.