All day long yesterday, the contrast between the two protests taking place in the City of London could not have been greater. Around the Bank of England where protesters were kettled by police the atmosphere was febrile, silent except for the clatter of the helicopters and the occasional rising chant: "Whose street? Our street!"

A few hundred feet down the road in Bishopsgate, however, it was a different story altogether, with music, drumming, dancing and face-painting. Climate Camp, having taken possession of this stretch of London road, proceeded to turn it into a mini-Glastonbury, complete with queues for the toilet and tent cities.

Which made it all the more shocking when, at 7.10pm, with no warning whatsoever, helmeted riot police suddenly marched towards the crowd and closed off the street.

Clamping together both ends of the protest simultaneously, they trapped several thousand people in the area, and used their batons in several places. "Why are they doing this?" said one of the Climate Camp legal observers who, like me, had ended up by chance on the outside of the kettle. "It's been completely peaceful all day long, there's no need for this at all."

In the scuffles that followed the police action at the Bank of England end where we stood, one policewoman was felled and had to be taken off for medical attention, while we witnessed several protesters being hit and kicked by police holding the line together.

The police slowly moved those outside the line back – using the same technique they had used by the Bank of England of kettling the central group and building up a large gap between them and any other protesters nearby.

Around 8 o'clock one protester, Dave from South Africa, stumbled towards the group: he'd attempted to sneak round police lines and had, he said, been forced face down into the ground, and had his wrists bent as far forwards as they would go. In a clear state of shock he said: "The police told me that I was lucky they weren't breaking my wrists, that I would feel this for three days." On the left side of his face was a bleeding gash from contact with the road.

The police had initially indicated that they would start to let people out after a couple of hours, but as the night wore on there was no sign of that beginning, and no information from the police. Observers were increasingly worried about protesters with small children, and the growing cold.

But inside the kettle the mood was, apparently, not too bad. The Bicycology group carried on playing music, there was a bit of performance poetry, and more dancing. "About 11pm," said one protester, Jenny Hill. "I started making a sandwich for a friend after the central kitchen had closed, and then discovered stashes of bread and peanut butter and jam, and ended up making about two hundred."

When the police finally began letting people out, at about 11.30pm, she was relieved to go home, but like other protesters could not understand the way police dealt with them. Another protester recounts the way that police at the end forced them out without giving them time to get their tents or belongings, after holding them there for five hours. "It was all done in a mood of violence," she said. "It had been really peaceful all day, so I don't understand why it had to end like that."

So it was a long day with a fairly miserable ending. The legality of the kettle is under scrutiny, and Climate Camp are still going through the process of finding out if there were arrests. It was never going to be a beautiful sunset, but most people believe it could have ended very, very differently.

What do you think?