Born the son of John Henry Jellicoe, a captain in the Royal Mail Steam Packet Company, and Lucy Henrietta Jellicoe (née Keele) and educated at Field House School in Rottingdean, Jellicoe joined the Royal Navy as a midshipman in the training ship in 1872 [REF].
Jellicoe qualified as a gunnery officer in 1883 and was appointed to the staff of the gunnery school in May 1884 [REF].