It is obvious the British police are incompetent in this respect. I don’t see even the most incompetent American policeman not completely searching arrested people before even putting them in the car.
I have had two friends who had pistols after being searched, one I was with and he threw it into a ditch (after being searched) before they put us in the car, and the other told me he was sitting handcuffed on the bench at the station in the awkward position of still having a pistol on him and not knowing how to handle the situation.