Admiral Sir John David Luce, was a Royal Navy officer. He fought in the Second World War as a submarine commander before taking part in the Dieppe Raid and becoming Chief Staff Officer to the Naval Forces for the Normandy landings. He also commanded a cruiser during the Korean War. He served as First Sea Lord and Chief of the Naval Staff in the mid-1960s and in that role resigned from the Royal Navy along with Navy Minister Christopher Mayhew in March 1966 in protest over the decision by the Labour Secretary of State for Defence, Denis Healey, to cancel the CVA-01 aircraft carrier programme.

The First Sea Lord and Chief of the Naval Staff (1SL/CNS) is a statutory position in the British Armed Forces usually held by a four star admiral. As the highest-ranking officer to serve in the Royal Navy, the chief is the principal military advisor on matters pertaining to the navy and a deputy to the Secretary of State for Defence. In a separate capacity, the CNS is a member of the Chiefs of Staff Committee and, thereby, a military advisor to the National Security Council, the prime minister and the monarch. The First Sea Lord is typically the highest-ranking officer on active duty of the Royal Navy unless the Chief of the Defence Staff is a naval officer. Admiral Ben Key was appointed First Sea Lord in November 2021.