Admiral Sir Nigel Richard Essenhigh is a former Royal Navy officer who served as First Sea Lord and Chief of the Naval Staff from 2001 to 2002. He served as a navigating officer before commanding the Type 42 destroyer HMS Nottingham and then the Type 42 destroyer HMS Exeter during the Gulf War. As First Sea Lord he entered into a contract to acquire up to 150 Joint Strike Fighter aircraft for the UK's two new aircraft carriers. In retirement he worked for Northrop Grumman and became a non-executive director of Babcock International. He remains a Deputy Lieutenant of Devon.

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.