The Royal Navy took a somewhat different approach to new submarine production immediately after World War II. Alone among Allied navies, it had direct experience in creating submarines with high underwater speed during the war, having converted several S class boats into high-speed targets for antisubmarine forces. It used that experience, plus additional information derived from study of the German elektroboote, to generate its own conversion program to build up a force of fast boats from recently completed T and A class submarines, while working to make more radical propulsion technologies reach production maturity.
The Admiralty looked into nuclear propulsion but decided to exploit the German Walther close-cycle turbine system for its non–air breathing submarines, because it seemed less expensive and closer to being ready for service. Unfortunately, British experts were under the impression that German technicians who had tested this system in a small number of experimental platforms were much closer to solving all of its problems than was really the case. The Royal Navy built two special experimental boats, the Explorer and the Excalibur, as platforms to bring the Walther system to production status; in the meantime, they built new conventional submarines that, while very reliable and generally quite effective, did not represent much of an advance on the conversions of wartime boats or the German elektroboote. The failure of the work in developing a mature Walther system left the Royal Navy no alternative but to turn to the United States for nuclear power technology when the time came for it to build its own submarines that would be free from the limitations of diesel-electric propulsion.
