Between 1935 and October 1938 he served on various submarines in the Home Fleet and Mediterranean Sea, before becoming first lieutenant on HMS Swordfish.

He then transferred to HMS Tigris, and on 13 November 1940 he was awarded the Distinguished Service Cross (DSC) for his actions during an engagement involving the submarine.

He was made a Companion of the Distinguished Service Order on 20 December 1942 for his successful patrols in the Mediterranean as commander of Porpoise, during which seven enemy ships were sunk.

On 11 April 1944 Bennington was awarded a Bar to his DSO for the successful attack on the Japanese cruiser Kuma during the action of 11 January 1944.

[6] On 20 February 1945 he was awarded a second Bar to his DSC for "outstanding courage, skill and undaunted devotion to duty" while in command of HMS Tally-Ho.