K-class submarines were designed to counteract a rumoured German ocean-going high-speed submarine. The whole class of seventeen were ordered from a variety of shipbuilders, and built in great secrecy before the first of class trials were carried out.

These submersible "destroyers" were the largest, heaviest and fastest submarines in the world at that time; in fact they proved to be so fast, that no British WWII submarine could have outstripped them. Conversely, no modern warship in any Navy ever suffered so much calamity as the K-boats. They were involved in sixteen major accidents and countless minor mishaps. One sank on trials, three were lost after collisions. A fifth disappeared and another sank in harbour. The loss of life was appalling. The admiralty persevered with the K-boats until 1923, even contemplating larger versions, K23 - K28, of which only K26 was built at Barrow, and fitted out at Chatham Dockyard. K26 survived until March 1931, when she was scrapped.

K26 was planned to be the first of the "follow up" to the earlier K Class. The hull was longer and she carried more armament, but her machinery was the same, which had the result that she was half a knot slower. The remainder of the class K23-K28 were cancelled as a result of the Washington Treaty regarding tonnage limitations. 1924, K26 successfully cruised to Columbo (Ceylon) and back.1931. Sold for scrap at Malta.