I love taking photographs around the world but recently, i have started to get the clear impression that people dont seem to like it and look very suspiciously at anybody taking photo's. Here's a great blogpost which explains the background to this. I quote some bits:
That this House is concerned to encourage the spread and enjoyment of photography as the most genuine and accessible people's art; deplores the apparent increase in the number of reported incidents in which the police, police community support officers (PCSOs) or wardens attempt to stop street photography and order the deletion of photographs or the confiscation of cards, cameras or film on various specious ground such as claims that some public buildings are strategic or sensitive, that children and adults can only be photographed with their written permission, that photographs of police and PCSOs are illegal, or that photographs may be used by terrorists; points out that photography in public places and streets is not only enjoyable but perfectly legal; regrets all such efforts to stop, discourage or inhibit amateur photographers taking pictures in public places, many of which are in any case festooned with closed circuit television cameras; and urges the Home Office and the Association of Chief Police Officers to agree on a photography code for the information of officers on the ground, setting out the public's right to photograph public places thus allowing photographers to enjoy their hobby without officious interference or unjustified suspicion.
Neither the Police nor PCSOs nor any private security guards, have any legal power at all to confiscate your camera equipment, film, digital storage media etc. in the street or public place, unless you are actually being arrested.
Even if you have been arrested, there are no powers whatsoever for a Policeman to erase, or to force you to erase film or digital storage media, and they might be committing an offence in doing so e.g. destruction of evidence or criminal damage.
A Court can, eventually, order the destruction of photographs, but that sort of situation does not apply on the street. It is a criminal offence to take photos inside a Law Court, of the defendants, judges, lawyers or witnesses (hence all the nonsense with "artists impressions" which appear in the mainstream media during high profile cases).