William Foster was born in 1884, the son of Montague & Mary Foster of Stubbington, Hampshire.  He joined the Royal Navy in 1898.

Promoted to Lieutenant in 1905, he was appointed to the Submarine Depot Ship HMS THAMES ‘for Training’ then to the Submarine Depot Ship HMS MERCURY ‘for Submarines’.  In 1907, he was appointed to ‘for Submarine A11 in Command’.  The following year he took command of HMS C16. In 1911 he returned to the Surface Fleet for his ‘Big Ship’ time firstly in the battleship HMS KING EDWARD VII and then the battleship HMS HERCULES from 1st August 1911.

He returned to submarines in 1912 and took command of HMS C13 and was promoted to Lieutenant Commander the following year. He subsequently had command of HMS D8 and HMS E6.  

E6 left Harwich on 26 December 1915 for a patrol in the North Sea. In the area of the Sunk Light Vessel, Lieutenant Commander Foster was warned by a patrol vessel to keep well clear but shortly afterwards E6 struck a mine and was sunk with all hands.

William Foster was the husband of Gertrude Searle Winter (formerly Foster) of Moray Cottage, West Byfleet, Surrey. He is commemorated on the Portsmouth Naval War Memorial on Panel No. 7.