I am afraid there are lengthy delays. We have applications in for 2 first adult passports – they should be straightforward but HMPO have decided not. Husband (born in Scotland, emigrated with parents to Australia as a child) applied for first UK passport 18 Feb and has been in processing since 14 April. Son’s was put in a couple of days later, also in processing since 14 April and needs dad’s birth certificate for eligibility.
There is no question of eligibility (our daughter got her passport with a 2 week turnaround in 2019 using same documentation as her father and brother!) but someone has decided to raise issues where there should be none, with documents they have previously accepted.
Hopefully you might have better luck. We are yet to hear whether an interview will even be required for either application, as they are busy quibbling about documents – problem is also the length of time it takes for documents to be processed in the mailroom, our initial documents sat there for 4 weeks.
I am of course wishing my husband had applied for his passport ages ago like his sister did, instead we are dealing with a bureaucratic mess.