Henry Priaulx Cayley was born on 29 December 1877 at Clifton, England. After attending Eastman’s Naval Academy, he joined the Royal Navy in 1891 as a cadet and was promoted regularly thereafter. Cayley was posted to the Mediterranean Station and later the Channel Fleet before serving on H.M.S. Undaunted during the Boxer Rebellion in 1899. In 1909 Cayley, now a lieutenant, was posted to the Australian Station, serving as the Royal Navy’s inspector of warlike stores. He resigned from the Royal Navy in mid-1912 in order to join the newly established Royal Australian Navy and was later appointed lieutenant-commander.
With the outbreak of the First World War in August 1914, Cayley was made an acting commander and sailed with the first Australian troopship convoy as transport officer on the troopship HMAT Euripides. Early the following year he was transferred to H.M.S. Isis and in April was promoted to the rank of commander. In March 1917 Cayley was appointed second-in-command of the light cruiser HMAS Sydney under Captain John Saumarez Dumaresq. Two months later, whilst the Sydney was patrolling the North Sea, Cayley wrote a letter to his mother detailing “an amusing and thoroughly entertaining two or three hours.” In the letter dated 23 May 1917, he described how the Sydney and her destroyer escort had encountered the German zeppelin L43 and several German submarines, and the attempt by Sydney to shoot the down the zeppelin whilst performing evasive procedures to avoid enemy submarine-launched torpedos. Cayley was promoted captain in April 1919 and took command of the Sydney.
After the war, Cayley served in a variety of roles including captain-in-charge at Flinders Naval Depot in Victoria, second naval member on the Australian Naval Board, commander of HMAS Melbourne, captain superintendent in Sydney, and naval representative on the Australian High Commissioner’s staff in London. He retired on 7 August 1931 with the rank of rear admiral. Henry Priaulx Cayley spent the remainder of his life in England and died at his home in Chelsea on 31 December 1942.