Sismore remained in the RAF after the war, qualifying as a fighter pilot and occupying several senior officer posts. In 1947 Squadron Leader Sismore and former Dambuster pilot, Squadron Leader 'Mick' Martin, broke the London to Cape Town flying record, covering the 6,717 miles in only 21 hours and 31 minutes. They were subsequently awarded the Royal Aero Club's Britannia Trophy for 1947. From 1953 to '56 he commanded No. 29 (Fighter) Squadron. Sismore was promoted to group captain in 1962, and from 1964 to 1966 he served as the Station Commander of RAF Bruggen in Germany. From 1966 to 1970 he was the Senior Air Staff Officer of the RAF's Central Reconnaissance Establishment at RAF Brampton.