In the UK there is no requirement to identify yourself to the police. From the
government website:
"Stop and question: police powers
A police officer might stop you and ask:
what your name is
what you’re doing in the area
where you’re going
You don’t have to stop or answer any questions. If you don’t and there’s no other reason to suspect you, then this alone can’t be used as a reason to search or arrest you."
If you're in charge of a motor vehicle you can be required to show your driving licence and car insurance documents, or present them at a police station by the next day.