Towards the end of WWII, the German scientist Dr. Helmuth Walther had developed a revolutionary new submarine propulsion system based on the highly volatile chemical High Test Peroxide (H.T.P.).

It was a steam generating plant, working on the principle that H.T.P. when passed over a catalyst produced oxygen and water. This was then fed into a combustion chamber, sprayed with diesel fuel, the resulting mixture generating steam that powered a steam turbine. When installed in a submarine, the operation of this new system was described as "exciting".One of the four Walther boats (U1407) built during 1945 was scuttled in Cuxhaven on May 5th 1945. Raised by the British in June 1945 and brought back to Barrow-in-Furness, to be refitted with a virtually new complete set of machinery, also captured in Germany.

The new boats for one reason or another were far to long in building, and in spite of achieving phenomenal underwater speeds for the day, they were overtaken by the American development of nuclear power for submarines. Consequently, these submarines followed their German forebear into Thomas Ward's breakers yard.

Although part of the 3rd Submarine Squadron, the two H.T.P. boats tended to operate independently, accompanied by their own depot ship HMS Kingfisher and a fuel carrier, the converted water-carrier, RFA (Royal Fleet Auxiliary) Spabeck.