It was an old piece of cultural shorthand, now almost lost to history: when her kid would ask who the strange man was who kept staying the night, the mum was supposed to explain "It's your uncle". A similar sexual subtext was given to the word "lodger". It would have been obvious to people who grew up in the war years that Pike was the son of Sergeant Wilson. His affair with Pike's mother out of wedlock was the key reason why Mainwaring was the bank manager and Wilson was the deputy.