On one of the lists I am on someone posted a link to a great website in response to a discussion of people being stopped from taking photos when there is no legal right to do so.

The link is here to Bert P. Krages web site. He is a lawyer who is also a photographer and has prepared a PDF document of your rights to photograph that you can carry with you incase of problems. It is for the US but a link to one for the UK is on his site.

Worth a look in this age of extreme paranoia and tendency to deny anything.