Alexander Cockburn was born in Portsmouth, Hampshire, on 18 May 1905, the son of Robert and Adelaide Cockburn. He joined the Royal Navy as an Engine Room Artificer Apprentice on 6 August 1921. After the completion of his apprenticeship, he served in the battleships HMS RESOLUTION & HMS WARSPITE. He also served in HMS WITCH and HMS ALRESFORD and, by 8 December 1928 he had been rated Engine Room Artificer Fourth Class, when he was drafted to HMS DOLPHIN ‘for the Submarine Course‘.

On 13 March 1929 he was drafted to HMS L25. He returned to HMS DOLPHIN ‘for the Spare Crew‘ on 22 August 1930 and next served in HMS ROVER from 2 October 1930 to 9 October 1934. Alexander Cockburn joined HMS H49 on 26 October 1934. This was followed by a draft to HMS STURGEON on 29 February 1936. He was promoted to Warrant Engineer on 1 October 1936 and, on 19 December 1939 he was appointed to the cruiser HMS DELHI.

Alexander Cockburn returned to submarines, when he was appointed the Submarine Depot Ship HMS TITANIA on 16 August 1938. He was then appointed to HMS SEAHORSE as Engineering Officer on 12 April 1939. In late December 1939 HMS SEAHORSE was sent on a patrol in the Heligoland Bight off the estuary of the river Elbe. On 7 January 1940, the German 1st Submarine Minesweeping Flotilla made an attack on a submarine – believed to have been HMS SEAHORSE.

Alexander Cockburn was the husband of Winifred Alice Cockburn of Cosham, Portsmouth. He is commemorated on the Portsmouth Naval Memorial on Panel No. 37 Panel No. 2