HMS H43 was built by Armstrong Whitworth, Newcastle Upon Tyne. She was laid down on 4 October 1917 and was commissioned on 25 November 1919. In World War 2,  H43 conducted four war patrols off the West coast of Ireland between 9 Nov 1939 and 31 May 1940.

On 6 July 1940, H43 (Lieutenant G.R. Colvin, RN) departed Plymouth for her fifth war patrol and conducted a special operation, delivering Lieutenant Hubert Nicholle to German occupied Guernsey to undertake a reconnaissance. On 9 Jul 1940, H43 departed for her sixth war patrol and conducted the second part of the operation, landing two reconnaissance agents (Second Lieutenants Martell and Mulholland) on Guernsey in the early morning hours of 11 Jul 1940, The agent landed on 8 July was taken off.

H43 then conducted seven war patrols off the French Coast and in the Bay of Biscay, between 14 Jul 1940 and 13 February 1942. This was followed by A/S exercises and RDF trials until she was decommissioned on 20 Sep 1944