The only external manifestations of ABC were two large aerials fitted on top of the Lancaster's fuselage and another under the bomb aimer's window. Trials with an ABC-equipped Lancaster were made on 4 September and the Squadron flew its first operation using the equipment on the 22nd during a raid on Hanover.
The targets in northern France were much closer than those normally visited by the Squadron but they could be just as tough as the raid on a German barracks at Mailly-le-Camp on 3 May proved. Five of the Squadron's Lancasters were shot down and only one man, a sergeant air gunner, survived the ordeal. Four days prior to the Normandy landings the Squadron participated in a very successful pin-point raid against an early warning radar station at Bruneval on the French coast near Le Havre. For D-Day itself the Squadron took part in an elaborate deception plan designed to lure the Germans into thinking that the invasion was about to take place in the Pas de Calais area.

No 101 Squadron provided 24 aircraft to simulate a bomber stream heading for Paris and to create an ABC barrier between the invasion forces in the west and the Luftwaffe's night fighters based mostly in Holland and Belgium. Other aircraft simulated convoys and airborne landings and jammed enemy radar and the whole effort was a great success. The Squadron only lost one Lancaster, which ditched in the English Channel through engine trouble, all the crew being saved.

An airborne radar set which could be carried in any aircraft and which displayed on a small screen in the navigators position a rough radar picture of the ground over which the aircraft was flying.

Mechanical failure was frequent, reception of the reflected impulses was often uncertain and confused, and above all the interpretation of what the navigator saw was difficult. One built up area could look just like another unless it had distinct radar properties such as well-defined river or coastline. The code name "Stinker" was suggested but soon changed to its permanent name H2S.

H2s could be used both as a navigational aid supplementing the navigators dead-reckoning and visual sightings and also as a blind bombing device. The latter always erratic.