I was in a pub in Kilburn (an area of London with a lot of Irish) some years ago, standing at the door on a warm evening. Three guys came out of the pub and suddenly vans erupted police with guns and pushed one of the guys against the wall - several guns pointed at his back. I had my camera with me, but thought it wiser not to point anything at police with guns in their hands. It would have made a great photo, especially as there was a poster just above the guy against the wall - for an Irish bank ! :-) Maybe it's because I'm a Londoner - that I moved to Nice.
Kilburn pubs I remember from years back, and they didn't have a safe sort of feel... You were no doubt very wise not to take pictures, you might have found yourself up against (the wall and) some mean and possibly Special Branch coppers.
As I remember it, the cops were very psyched up - now one thinks of the case of the young Brazilian shot on suspicion in the tube in London. This was the time of the conflict in Northern Ireland - and with any sudden movement one of them might have shot first and asked what I had in my hands afterwards - especially as it was a SLR - not the friendly little Lumix :-) Maybe it's because I'm a Londoner - that I moved to Nice.