If you're waiting to cross the road, the lane of traffic nearest you is stationary, and the light showing for traffic is still green (implying that the light for crossing is still a red man)... then do not assume that it is safe to cross. Because cars in the next lane cannot see you and will be approaching.
This was demonstrated by the chavs at the Quay Street Roundabout - this particular crossing has three lanes entering the roundabout, the right-most lane was waiting behind the stop line because their lane on the roundabout was full (not because they were giving way to pedestrians or because of the lights), the lights were green, and the other two lanes were empty. So the chavs decided to cross the road right in front of me as I was approaching in the middle lane. Fortunately we all stopped in time to avoid a collision.
Of course, the chavs then yelled at me because "the other cars stopped", despite the light still being on green for me and red for them. Congratulations, you fail at crossing the road.