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.
Oh yeah, they do that all the time. I have dual citizenship and they’ve asked me a few times upon leaving the UK where I was staying, who I was with, what those people’s professions were, etc. I think it’s just random spot-checks to see if you look nervous. But if you get annoyed with them and tell them you’re a citizen they stop.
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.