De Havilland Mosquito
Immediately after being commissioned, in December 1942 he joined No. 105 Squadron, navigating a De Havilland Mosquito alongside pilot Squadron Leader Reginald Reynolds. Over the following 20 months, the pair would see little rest and make some of the most daring targeted raids of the war, which came in retrospect to recognise Sismore as the RAF's finest low-level navigator of World War II.