In 1927, while serving on HMS Argus, he took part in the western military buildup in the Far East when European interests in Shanghai were threatened by fighting between the forces of Chiang Kai-shek and the warlord Sun Chuan Fang.

In June 1931, Fancourt was involved in trials, aboard Courageous, of a new system of athwartships arrester cables to catch landing aircraft.

In December 1940 he was promoted Captain and given command of HMS Sparrowhawk, the naval air station at Hatston in the Orkney Islands.

In May 1941, he was Mentioned in Despatches for his initiative in sending a Maryland aircraft to reconnoitre for the German battleship Bismarck after poor weather had prevented RAF reconnaissance.

He also ordered 828 Naval Air Squadron's Albacore torpedo bombers to Sumburgh, ready for a strike on Bismarck should she come within range, but she did not.

[1] While at RAF Hatston in Orkney in April 1942 Fancourt, flying a Gloster Gladiator, is claimed to have made the first landing of the war by a British plane on an American aircraft carrier when the USS Wasp was passing through Scapa Flow, however Lt Basil Boulding of 812 Sqn has a better claim as he landed Swordfish P4219 aboard the USS Wasp from RAF North Front, Gibraltar, eventually disembarking at RNAS Macrihanish prior to the USS Wasp's arrival at Scapa Flow and joining Force H.[2] In 1942, Fancourt had been assigned to take command of the escort carrier HMS Searcher, then under construction in the United States.

The assignment was to enter Algiers harbour on 8 November, land the troops and prevent the Vichy French from scuttling their ships or wrecking the port installations (Operation Terminal).

He was retired from the Navy in 1951, not having been promoted to flag rank due to his lack of "sea time", in other words insufficient experience aboard ship.

Both sons were in the Navy - Michael served in the Fleet Air Arm, and Rodney, who predeceased his father, was a captain in the Royal Naval Reserve and commanded London Division RNR.

In 1943, Fancourt landed a Fairey Swordfish with Michael, then a 16-year-old Air Training Corps cadet, as a passenger, on HMS Argus.