Although the Thames Class design proved successful in service, it was soon realized that the concept was wrong, and with its passing it became apparent that, with surface capital ships being capable of 30 knots, underwater speed was to be a principal feature of future submarine designs.
In conjunction with the Fleet Submarines, 12 Small Patrol Submarines were ordered in February 1929 (eight from Chatham, three from Cammell Laird and one from Scotts) and were the forerunners of the famous S Class submarines that served so effectively in the Second World War. Called the. Swordfish and Shark Classes, they were based on the saddle-tank construction of the L Class submarines, the majority of which were built by Vickers ten years earlier.
