Both I and others on the Lib Dem Voice team have covered various stories about people being questioned by the police for taking photos.
So here’s the guidance from the National Policing Improvement Agency,* contained in their 2008 guide, Stop and Search in Relation to Terrorism:
The Terrorism Act 2000 does not prohibit people from taking photographs or digital images in an area where an authority under section 44 is in place. Officers should not prevent people taking photographs unless they are in an area where photography is prevented by other legislation.
If officers reasonably suspect that photographs are being taken as part of hostile terrorist reconnaissance, a search under Section 43 of the Terrorism Act 2000 or an arrest should be considered. Film and memory cards may be seized as part of the search, but officers do not have a legal power to delete images or destroy film. Although images may be viewed as part of a search, to preserve evidence when cameras or other devices are seized, officers should not normally attempt to examine them. Cameras and other devices should be left in the state they were found in and forwarded to appropriately trained staff for forensic examination. The person being searched should never be asked or allowed to turn the device on or off because of the danger of evidence being lost or damaged.
Quoting the last sentence might be fun if you are filming, asked by the police to stop and say that you’d like to film them questioning you…
* If you’ve not heard of them before, their guidance, “is commissioned by ACPO or the Home Office and is produced primarily to assist practitioners by promoting good practice … Practice Advice is a discretionary tool for chief officers as it identifies good practice. It may, however, underpin HMIC inspection frameworks and, therefore, chief officers may be accountable to HMIC if they do not follow it.”