Reminds me when I went to pick up my first UK passport when I gained citizenship. The passport office had no interest in looking at my foreign passport to verify my identity. Instead they asked me a series of question about my family, what profession they have, etc, that I know they couldn't have the answer to, unless they did some investigations that I think were highly unlikely given the volume of applications after the Brexit vote.

I think instead they were just checking if I looked like I was answering the question confidently or if I looked like I was trying to make things up.