Well they do if they are doing stop and search.
When the police stop and search you, they must provide you with the following information before the search can begin:
proof of their warrant card
information on police powers to stop and search
information on your rights
the police officer's name and police station
the reason for the search
what they think they might find when they search you.
https://www.citizensadvice.org.uk/law-and-courts/legal-system/police/police-powers/