Know Your Right in THE UK
Freedom to photograph and film
Members of the public and the media do not need a permit to film or photograph in public places and police have no power to stop them filming or photographing incidents or police personnel.
source: http://content.met.police.uk/Site/photographyadvice
Stop and question: police powers
A police officer has powers to stop you at any time and ask you:
what you’re doing
why you’re in an area and/or where you’re going
However, you don’t have to answer any questions the police officer asks you.
Stop and search: police powers
A police officer has powers to stop and search you if they have ‘reasonable grounds’ to suspect you’re carrying:
illegal drugs
a weapon
stolen property
something which could be used to commit a crime, eg a crowbar
You can only be stopped and searched without reasonable grounds if it has been approved by a senior police officer. This can happen if it is suspected that:
serious violence could take place
you’re carrying a weapon or have used one
you’re in a specific location or area
Before you’re searched
Before you’re searched the police officer must tell you:
their name and police station
what they expect to find, eg drugs
the reason they want to search you, eg it looks like you’re hiding something
why they are legally allowed to search you
that you can have a record of the search and if this isn’t possible at the time, how you can get a copy
source: https://www.gov.uk/police-powers-to-stop-and-search-your-rights