[1] During his time as Commandant ROC, Sismore travelled overseas to France, Germany and Scandinavian countries, visiting similar defence warning organisations.
He established a close relationship with the Luftmeldekorpset Danish Air Reporting Corps, a unit of the country's Home Guard.
Educated at Kettering County School, on the outbreak of the Second World War Sismore started his service as an airman in the Royal Air Force Volunteer Reserve (RAFVR).
However, on 29 August 1942 Flight Sergeant Sismore was given an emergency commission as a General Duties Branch pilot officer in the Royal Air Force Volunteer Reserve.
[4] On 30 January 1943, the pair led the first of two Mosquito raids on Berlin timed to disrupt speeches being delivered by Reichsmarschall Hermann Göring and Joseph Goebbels, the Third Reich's Propaganda Minister.
IVs from 105 Squadron, which attacked Berlin's main broadcasting station of Reichs-Rundfunk-Gesellschaft on Wilhelmstrasse at 11:00,[5] when Göring was due to address a parade commemorating the 10th anniversary of the Nazis' being voted into power.
Goering himself was not amused; six weeks later he harangued aircraft manufacturers that he could "go berserk" when faced with the Mosquito, which made him "green and yellow with envy.
"[6] For the rest of the spring, the pair mostly led strategic daylight raids against key targets, including power stations, steelworks and factories, and railway assets.
140 Wing, Sismore, by then an acting squadron leader, took part in Operation Carthage, a precision raid on the Gestapo headquarters in Copenhagen, Denmark.
[8] The raid, while not being completely successful with a large number of civilian casualties, succeeded in destroying the Gestapo HQ allowing some prisoners to escape.
In March, 1945, Squadron Leader Sismore was the navigator in the leading aircraft of a large formation detailed to attack the Gestapo headquarters at Copenhagen.