The protest was entirely peaceful, albeit a bit vocal, until the first red smoke bomb was set off on the corner of Parliament Sq and Great George St next to the traffic island at 14:57:30. Following the smoke, several tomatoes, sticks, bangers and other bits and pieces were thrown whilst a group of demonstrators with makeshift polystyrene shields turned right and faced down the police line.
The police had their batons drawn, but they weren't used for the first time until their line was in danger of being breached, and even then they were taps rather than a full blown swipe.
There was no chance in hell that it was ever going to be a peaceful protest.