Taking photos, especially in public places, is not always legal. Even in this domain, if you don’t play by the rules, you risk breaking the law and losing your camera.
Concerning this matter, the attorney Bert Krages created a flyer, “The photographer’s right”, which you can download at www.krages.com.
You can also check out www.usatoday.com and www.andrewkantor.com for more information on this subject.
The basic principle on this matter underlines the fact that anyone in a public place can take pictures of anything they want. If you are, however, on a private property, and are asked not to take pictures, you have to obey. You can photograph any person on a public domain, if their activity doesn’t imply a certain degree of privacy (for example, when someone enters their PIN at an ATM). Otherwise, you can photograph anything, from criminal activities to celebrities and accidents.
You do not have to explain why you where taking pictures of something, when challenged, and you don’t have to give your camera to someone who tries to confiscate it, except when, in both cases, the person in cause is a law enforcement officer, but even they need a court order to confiscate things.
Still, if you are respectful and polite, you shouldn’t face any serious problems in this type of situations.
Further details about the situation in the UK can be found here:-
http://photographernotaterrorist.org/