The submarine design which had been chosen by the Admiralty for the Royal Navy was the American Adder Class - a new design from the Irish-American J P Holland which had not yet been built. Construction of the British boat was therefore in advance of its American counterpart. Consequently, the many problems which were encountered at Barrow had no precedent but Vickers were not allowed to make changes without infringing the performance guarantee. Indeed, it was only after the boat nearly turned turtle in Barrow docks with a supposed American 'specialist' from Holland Boat and a member of the British Admiralty on board that Vickers was given free rein to make necessary changes to the design.
