I was just curious as on the first adult specific application page it says:
You can apply for a first adult passport if all of the following apply:
you’re a British national
you’re aged 16 or over (or will be in 3 weeks)
you’ve never had a UK passport before
Which implies there is a difference if you’ve NEVER had a passport before vs having an out of date child one. On the first adult passport page it says you’ll need someone who can confirm your identity and supporting documents, but doesn’t on the generic application page.
On the genetic application page it asks you to send the old passport in (and it asks how old you are when it was issued so they know how old it is but still ask for it) I’m thinking that this could remove the requirement for someone who can confirm your identity and having to send supporting documents / possibly the (soft) requirement for an interview – still a first adult passport but maybe with fewer steps?