Not at all related to flight crew interviews, but was at a university interview for Aeronautical Engineering...
Q: What is this, and what function does it play?
I was then handed a 2 inch square piece of aluminium that could have quite literally come from any part of the aircraft. However, asking the interviewer after the interview, they weren't necessarily looking for the correct answer, just wanted to see how you went about deducing what is could be.
It turned out that the aluminium was in fact a tiny section of fuselage and this could be told by the spacing between rivet holes!
Now I know that BA aren't likely to do that, but still be prepared for anything and if you don't know, say but do deduce what it might possibly be!!!! They want to see how you think.