Anyway, this is What Actually Happened in Trafalgar Square, not sponsored by the Met Police's PR team.
I'm sketchy on times but fairly late in the evening the samba band arrived at Trafalgar square and it was filled with about a thousand people, drinking and dancing, talking and drawing on the flagstones with chalk. It wasn't a protest so much as a large after-party. Most people there were young - university and FE students and recent graduates. I think anyone who'd read the "turn Trafalgar square into Tahrir!" event title would have felt a bit disgusted comparing this to events in Egypt. But it wasn't violent, and there was still an atmosphere of defiance and unity and happy chaos. We weren't so much protestors as post-protestors. The band played a set and were surrounded by a cluster of jumping, screaming students chanting "we all hate the cuts, we all hate the cuts!" along to our drumbeats. Fireworks shot up into the sky at the cresendo of every song.
When we finished playing, the band started drifting away to home or the pub, and I walked over to a group of people I knew on the steps, to catch up and compare notes on the day. I was chatting to one of them when I was pushed aside by a group of around four policemen who dived in and grabbed a masked guy a few metres away from me. People shouted "what are you doing?!" and they responded "he just threw a paint bomb." Everyone on the steps began chanting "shame on you! shame on you!", and people pushed their way forward to grab the arrested guy's arms and pull him away from the police. The minute he was free, he bolted to safety, and suddenly the crowd was surrounding the police officers. Instead of listening to instincts of self-preservation they began chanting "who's kettled now? who's kettled now?"
The difference between police kettling protestors and protestors kettling police, of course, is that police have a large number of mates outside the kettle to help them out. And these mates decided that the only reasonable response to the affront was to clear us out of the square.
Within less than two minutes Trafalgar was filling with lines of helmeted, sheild-carrying police who had been parked just off the square waiting for something to kick off. I ran up to the plaza in front of the national gallery to find the rest of the band; most had gone but a few were left. A line of police advanced, blocking us off from the exit up to Haymarket, and a small group sat down in front of the line with our hands raised chanting "this is a peaceful demonstration! this is a peaceful demonstration!" The police ordered us to get up and move and at first we refused, but when we realised it was turning into a kettle me and two friends decided to get to the other end of the square fast. We leaned over the edge of the balustrade and down in the main part of the square chaos was breaking out. I saw a girl I knew backed up against a wall by a policeman with his baton raised. Another girl, clearly injured, was carried out of the crush by a few police and dumped at the base of the steps, crying. Protestors - they were clearly protestors now, protesting not the cuts but their being forced out of the square - responded by throwing anything they could find. Then another line pushed us out onto the road, out of sight of what was going on. A police line formed along the road, blocking us off from whitehall and charring cross. We were across the road from St Martin's, and a lot of people had gathered on the church steps, not sure where to go. A clutch of police burst out of the line, grabbed a guy in a hoodie, and pulled him back behind the line out of sight. In a moment of calm a girl started hitting my friend's drum and laughing: "sorry, I'm causing a scene!" "There's already a bit of a scene here." "Hmm, point taken!" It was then that some idiot had a bright idea: recycling bins full of empty bottles made great ammunition stores.
It had been dangerous before, but now it was deadly as the bottles flew through the air and exploded in shards on the road. A small group of seven or eight people stood down a side road, throwing the bottles overarm towards the police line. Everyone else was diving from place to place, trying to avoid the violence but not wanting to leave - we all had friends trapped in the middle of the chaos, and we were outraged at being driven from the square. A rubbish bin was burning. We saw another friend on the steps of St Martin's, and ran to join him.
This is the really controversial bit and I will accept a tiny possibility that I misread the situation, but it seems extremely unlikely. The people on the steps were not throwing anything, they were observers, wanting to get to safety but not sure they could, wanting to check their friends were OK. I didn't see anything thrown by anybody on the steps. The sensible thing for the police to do to do would have been to push us out towards the national portrait gallery, or even to kettle us - fine.
That isn't what they did. Instead a line of police pushed us off the steps into the firing line. In effect they forced us to stand between them and the bottle-throwers.
If it was really a tactic to try to stop the violence by the use of effective human shields, they failed miserably. Neither the police nor the kids throwing bottles really gave a shit if people got caught up in the fight. We made it a few metres before pressing ourselves up against the railings; I looked up, thinking I was safe for a second, and saw a bottle falling towards us. I just had time to think "50-50 chance which one of us it's going to hit" before it landed and shattered less than a foot from my head. I felt shards of glass land in my hair. Time froze for a second and then my friend shouted "RUN!" and I pelted up the road until I was out of the firing line. Seconds later my friends joined me. The bottle-throwers were trying to build a barricade out of recycling bins. An old man standing in the crowd shouted "why don't you go join them then? why don't you fight with them?" Tourists, Londoners and commuters were dragged into the chaos and had to run back when they realised what was happening.
From then on it was a mess - advancing groups of helmeted police and TSG pushing us aside or charging us every few minutes, and in the moments of calm desperately calling around everyone we knew in the square to check we weren't leaving anyone behind. Most people just didn't pick up their phones. At one point we were baton-charged and had to race up the Strand a few metres - luckily my friend who was carrying a heavy drum was out of the way at that point. A few minutes later another squad of police dived in to arrest a man, kicking my friend to the ground along the way. A man on crutches, knocked down onto the concrete, struggled to stand.
We were debating whether to leave or to stay and try to help people when my friend looked at her phone and screamed "run, we have to run, NOW!" She'd had a text that a line of police were about to block the Strand off, leaving us without any exit. We dived into a shop doorway with another ten or fifteen protestors to avoid yet another police charge and when we stepped out, the Strand was blocked. Police started their old routine: "you can't go out here, the exit is over there." "What, where the RIOT is?" Exhausted and furious, we started with the standard response "but we just want to go home. We just want to leave." The commander evidently took pity on us and said "let these guys out. Just let them go." We collapsed out onto the Strand. Just a few hundred metres away, people were sitting in restaurants, and drinking cans of cider on the street, enjoying a normal Saturday night.
What happened last night was the definition of escalation. We provoke the police. They respond disproportionately. Some of us respond peacefully, sitting with linked arms in front of the police line - some of us stupidly and brutally with glass bottles. The counter-response catches us all up in the cycle of violence. All this started with one paint bomb.