To be fair it has been a very specific issue in this country over the past several years that had some high profile complaints and protests, causing some embarrassment to the country:
2009 Police delete tourists photos:http://www.guardian.co.uk/uk/2009/apr/16/police-delete-tourist-photos
It was down to the interpretation of a specific piece of anti-terrorist legislation (section 44 of the 2000 anti terrorist act (we all know why) that was obviously too vague and was causing civil rights issues.http://en.wikipedia.org/wiki/Terrorism_Act_2000#Section_44The most commonly encountered use of the Act was outlined in Section 44
which enables the police and the Home Secretary to define any area in the country as well as a time period wherein they could stop and search any vehicle or person, and seize "articles of a kind which could be used in connection with terrorism". Unlike other stop and search powers that the police can use, Section 44 does not require the police to have "reasonable suspicion" that an offence has been committed, to search an individual.
In 2009, over 100,000 searches were conducted under the powers, but none of these resulted in people being arrested for terrorism offences
. 504 were arrested for other offences.In January 2010 the stop-and-search powers granted under Section 44 were ruled illegal by the European Court of Human Rights
That specific anti-terrorist legislation has been recently removed but I guess it takes time to unwind something like that, some officers may still over step the mark as anti-terrorism paranoia is still there to an extent. I think a wider more specific issue is of jobs worth private security personnel who are looking to make themselves seem important. The law in this country is very specific that private security personnel have no authority on public land and there are no laws against taking photos from public land. This may need further clarification as over the past 20 years the amount of privately owned publicly accessible land in the UK has ballooned.
The Met (London) police have to issue guidelines to police officers and soothe the photographing public on the matter: http://www.met.police.uk/about/photography.htm
Quoting from their 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.
However I also agree that if you consider how many tourists are in the UK photographing everything and how popular photography has been here for over 100 years, to stumble across a police office who mis-interprets anti-terrorist legislation or an over-zealous private security person would be bad luck rather than the norm.