Passport Interview

I would assume based on experiences with similar documents that it involves proving you are who you say you are.
There are numerous official government sources advising on what it involves:
https://mybritishpassport.com/uk-passport-interview/
https://www.gov.uk/apply-first-adult-passport/after-you-apply
https://www.gov.uk/government/publications/interviews-overview-of-the-interview-process/interviews-overview-of-the-interview-process-accessible-version
(last one for those conducting the interview so you'll see what is involved from the other side)

What’s your name, spell it. Where do you live, how long for. What’s your postcode. How many bedrooms in your house. What’s your parents names, birthdates, where were they born, etc. Who do you bank with. When did you sit your driving test.
Even stuff like - where do you work (or study) and how do you travel there? How long does it take? What is/was your school uniform like (I guess this is only asked to younger applicants, not 50yr olds applying for their first adult passport). Note that you’ve not been under surveillance for this, but it helps to show that you really live where you say you live, and have done for the amount of time you say you have.
If you’ve lived here all your life (and assuming you are actually a citizen by rights), you’ll be fine.
-copied from reddit.
Good luck, I hope it goes well <3