Under The Immigration (Hotel Records) Order 1972, those who are not British or Irish citizens are legally required to provide their passport details to UK hotels when checking in. They are also supposed to inform hotels where they are going next. Even though seeing an actual passport is not strictly required, in practice most UK hotels will ask to see ID from anyone whose booking does not contain a UK (or possibly Irish) address.

The only UK hotel to ever require my ID has been the Hilton Liverpool. A few times, perhaps due to racial profiling, I was asked for ID but I stated I was a British citizen and they accepted that without asking for proof.

I know of someone who was denied check in, but an emailed photo of the driving licence was eventually accepted.