To anyone who’s still worried in this forum, I hope my experience below will provide some info.
Application is for a first adult passport following naturalisation. I submitted my naturalisation certificate and current foreign passport.
This week I also called HMPO every other day and submitted enquiries using the online form stating that I needed a passport back (either the British one or my foreign one) in time for a mandatory appointment on 1 April. Not sure if my persistence helped but it’s all one can do. I was also promised call-backs that never materialised.
Application approved – 11 March 2022
Application being processed – 23 February 2022
Documents received – 13 February 2022 (note that Royal Mail delivered the documents on 4 February)
Application received – 31 January 2022
Identity details received – 31 January 2022
Email sent to person confirming your identity – 31 January 2022
Ask someone to confirm your identity – 31 January 2022
Application submitted – 31 January 2022
Now let’s just wait for the next stage of the stress – i.e. dealing with TNT etc.