The Royal Navy had been researching designs for nuclear propulsion plants since 1946, but this work was suspended indefinitely in October 1952. In 1955, the United States Navy completed , the world's first nuclear-powered submarine. During subsequent exercises with the Royal Navy, "Nautilus" demonstrated the advantages of the nuclear submarine against British anti-submarine forces, which had developed extensive anti-submarine warfare techniques during the Battle of the Atlantic. The Admiralty appreciated the utility of such vessels and under the drive of the First Sea Lord, Admiral The Earl Mountbatten of Burma and the Flag Officer Submarines, Sir Wilfred Woods, plans were formed to build nuclear-powered submarines.