Thanks for all your replies.
My wife and I are both dual citizens (AU & UK) so the child will automatically have both Australian and British citizenship at birth.
I will as you say get a copy of their Australian citizenship certificate.
Ultimately I will get the child a British passport, the question is simply if we do it before we return, or after in order that we can return sooner.
My fear is that the UK passport will take a long time. We already have one child and when I applied for their British passport back in 2021 it took 4 months which is a lot longer than advertised / a lot longer than it takes to get an AU passport.
If anyone has recently applied for a British child passport from overseas can you tell me how long the application took?
Also, if anyone has brought their child into the UK on a foreign passport, then applied for a British passport after you’ve returned I’d love to hear your experience.
Thank you!