Not really but here are some guesses:
Enemy alien incarcerated in a detention camp on the Isle of man for the duration of the war.
Working in Germany in 1939 and incarcerated by the Germans.
A foreign national (from a "friendly" country) working in this country who had their own ID eg passport.
I did wonder if in some branches of the armed force the paybook was accepted as ID.
I don't know - please tell.
Alan