Naval career
Having decided on a career in the Royal Navy, he proceeded to the Royal Naval College, Dartmouth. The year after entering Britannia, he went to sea as a midshipman aboard HMS Crescent. Having been an acting sub-lieutenant, he was confirmed in the rank of sub-lieutenant in October 1902, before being promoted to lieutenant in October 1904 while serving aboard HMS Caesar. In 1906, he was selected to specialise in gunnery. He subsequently served as a gunnery officer aboard HMS Dido, HMS Duke of Edinburgh, and HMS Grafton.
Lyon served throughout the First World War as gunnery officer on board HMS Monarch, during which he was present at the Battle of Jutland. In the closing months of the war, he was promoted to the rank of commander in June 1918. Following the end of the war, he was appointed to the Naval Ordnance Department at the Admiralty in February 1919, before being appointed commander of Portsmouth Barracks in 1921. Lyon was promoted to captain in December 1922, and from 1923 to 1925, he was an assistant director of plans at the Admiralty. From there, he spent two years commanding the 2nd Destroyer Flotilla in the Mediterranean. He returned to the Admiralty as director of physical training and sport in 1927, where he spent two years. From there, he was sent to Greece in 1929 as head of the British Naval Mission to the Hellenic Republic; following the conclusion of his appointment, Lyon was made a Commander of the Order of the Redeemer by the Hellenic Republic.
Lyon attended various senior officers' courses during the early 1930s and was promoted to commodore in July 1932, at which point he was appointed commodore commanding Home Fleet destroyers aboard HMS Centaur. He was promoted to rear admiral in November 1934, and in 1935 he was placed in command of the 3rd Cruiser Squadron until 1937. He was made a Companion to the Order of the Bath in the 1936 New Year Honours. He was decorated by Portugal with the Military Order of Aviz (Grand Cross) in 1938. He was appointed Commander-in-Chief, Africa in April 1938 (one year prior to its reorganisation into the South Atlantic Station), holding this appointment during the opening years of the Second World War. In October 1940, he was appointed a Knight Commander of the Order of the Bath. In 1941, he was appointed Commander-in-Chief, The Nore, and was promoted to admiral in June 1942. He held the post of Commander-in-Chief, The Nore until July 1943 and retired the following month, having been declared medically unfit for service.
