Fairmile D dog boats and flexible coastal warfare

The Fairmile D was designed to combine motor gunboat and motor torpedo boat work in a hull that could be reconfigured between roles. Its wartime uses expanded further to anti-submarine patrols and long-range recovery of downed aircrew, followed by postwar fast-patrol service. Although its roughly 29-knot full-load speed looked modest beside 40-knot torpedo boats, it retained speed better in rough water and could catch nominally faster German S-boats when conditions deteriorated. Scallops in the hull sides allowed torpedo launches, but visible hull form did not always reveal the current armament because weapons could be swapped. The six-pounder began with manual loading and later gained a Mullins autoloader. Six-pounders, 20 mm Oerlikons, machine guns, and depth charges made the D a powerful ambush predator and escort rather than a single-purpose speedboat.