The police were a reserved occupation. When Bomber Command was taking such high casualties that they were having difficulties replacing lost crews policemen were permitted to enlist but it had to be as aircrew. When this happened my father who had been a detective in the Blackpool police joined up and flew as Flight Engineer/Second pilot in a Lancaster.
I’m not sure when that happened, I’m guessing it must have been 1943 because I think Dad was bombing in 1944 and it took some months to train volunteers.
He survived the war and went on to lead a team of investigators into the war crime of the murder of the 50 officers who escaped from Stalag Luft lll, the Great Escape camp. He personally arrested 20 of the SS criminals and I think 11 were hanged. He got a military OBE for that.