Stella Rimington, the first female head of MI5, and also the first to be named in the press, revealed this interesting anecdote from the late 1970s when she published her autobiography in 2001:
They sent me on the newly created agent-running course… The first thing students on the course had to do was go to a given pub, strike up a conversation with anyone there and try to find out all about his private life. I say ‘his’ because when I got to my designated pub, somewhere near Victoria, there were no women in the bar. You obviously had to be prepared to give a fictional cover story about yourself in case the person was inquisitive. What you were not told was that, while you were doing this, someone from the course would arrive and recognise you, address you by your real name and do his best to blow your cover story. For a female, of course, faced with a bar full of males, this was particularly difficult.
Having read this, we’ll now feel very paranoid any time a stranger speaks to us in Cask.