photography and the law - taken from the Met Police website:

Freedom to photograph/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.

Photography and Section 43 of the Terrorism Act 2000

Officers have the power to stop and search a person who they reasonably suspect to be a terrorist. The purpose of the stop and search is to discover whether that person has in their possession anything which may constitute evidence that they are a terrorist.

Officers have the power to view digital images contained in mobile telephones or cameras carried by a person to discover whether the images constitute evidence that the person is involved in terrorism. Officers also have the power to seize and retain any article found during the search which the officer reasonably suspects may constitute evidence that the person is a terrorist. This includes any mobile telephone or camera containing such evidence.

Officers do not have the power to delete digital images or destroy film at any point during a search. Deletion or destruction may only take place following seizure if there is a lawful power (such as a court order) that permits such deletion or destruction.