Admiral of the Fleet Sir Rhoderick Robert McGrigor, was a senior Royal Navy officer. He fought in the First World War and saw action during the Gallipoli Campaign and then the Battle of Jutland. He also served in the Second World War, taking part in the sinking of the Bismarck in May 1941, carrying out the office of Assistant Chief of the Naval Staff (Weapons) and commanding the 1st Cruiser Squadron during operations off the Norwegian coast and convoys to North Russia. Furthermore, he served as First Sea Lord in the early 1950s and is most remembered as a leading proponent of carrier-based air power.

Admiral of the Fleet is a five-star naval officer rank and the highest rank of the Royal Navy, formally established in 1688. The five-star NATO rank code is OF-10, equivalent to a field marshal in the British Army or a Marshal of the Royal Air Force. Apart from honorary appointments, no new admirals of the fleet have been named since 1995, and no honorary appointments have been made since 2014.