Since I'm going to London in a few weeks and since I chatted with a guy on Facebook who had been confronted with security guards while photographing the Tower Bridge, I thought that I should share this video and a link to the guidelines of the ACPO (Association of Chief Police Officers) so that anyone planning on going to London can have a look at it.
To be honest, security guards seems to be a bit of a pain in the ass in this city and clearly have no real clue of what the laws are and what you can do in a public place. In a private place, they have the rights on their side, but in a public place, they simply don't. Watch the Youtube clip, it's very interesting.
And below is the link to the guidelines to the ACPO. Segment 4.38 is the key and I'm gonna print and bring this with me. But if you watch the Youtube clip, you'll see that the police are totally cool with everything, it's just the security guards that are a bit cunty. :)