In an answer to a question on entering the UK as a non-National, there was this interesting snippet of information:
Even Brits are subject to portions of the landing interview.
I'd always sort of assumed that a British National entering the UK on a British Passport wouldn't be subject to any sort of landing interview, just a comparison (by officer or e-gate) with the passport photo and potentially a scan of the passport.
So, what portions of a landing interview would apply to a British National entering the UK, and what (if any) documentation might they want to bring beyond their British Passport?