A group of photographers in London have investigated how easy it is to shoot around the city. The six photographers, backed up with six videographer, attempted to take photographs around the City of London (the city's financial district), to see what resistance they encountered. The experiment, conducted as part of the London Street Photography Festival, showed several private security guards trying to impede the photographers (often with vague allusions to 'security and 'terrorism'). The Police were called in three cases, but, in each instance, the Officers were well aware of the laws concerning photography and appear to have resolved the situations amicably. (via PetaPixel) 

Link to video: http://youtu.be/FJH9F7Hcluo