Standing on the steps of St. Paul's Cathedral, a young man addressed the 'Occupy London Stock Exchange' protest on Saturday. "There is a police line to my left", he said as the crowd repeated his words in unison to create an 'echo microphone' that allowed everyone to hear, "and we must be careful not to let it move forward." His warning proved prescient.

When the demonstration first assembled outside St. Paul's, it was largely unhampered by policing. I had arrived two hours earlier, and had witnessed the closing of Paternoster Square, the intended site of the occupation. But while the square, a private development and home to Goldman Sachs, was blockaded by police officers and horses, the assembly at St. Paul's was left alone. After it became obvious that Paternoster Square was unreachable, this became the new site of the occupation.

By 1pm, police had begun to line the edge of the crowd. Most were engrossed in the 'general assembly', a mostly democratic system of organisation by vote and hand-signals (wave one hand for 'yes', cross both hands for 'no'). It was already clear that the police intended to form a kettle, and form a kettle they did.

The protest was predictably peaceful. When the crowd first attempted to enter Paternoster Square, a small chant of "get those animals off those horses" briefly emerged (referring to mounted officers), but this was shouted down. "The police are not the problem", one man said, and the chant changed to a more sympathetic "your job's next". Throughout the day, music, dancing and football defined the mood. Why then was the protest kettled at all?

The standard answer is that kettling ensures that demonstrations remain static, and thus reduces the risk of injuries. Indeed, the police erected a screen which rolled the message "this area is contained to avoid breach of the peace" in deep red letters. Such is the irony of the idea that it's necessary to surround peaceful demonstrators discussing, dancing and singing, with officers equipped with riot helmets in order to maintain peace, it's surprising the screen didn't short-circuit.

But in any case the standard answer clearly doesn't apply to Occupy London; for the majority of the day, demonstrators were free to leave the kettle (at one small cavity). Instead it served to keep the hundreds of people who wished to join the occupation from doing so. Wikileaks founder Julian Assange was prevented from entering the demonstration for over an hour.

Furthermore, the Met issued statements throughout the day 'urging peaceful protesters to leave' St. Paul's. They even resorted to claiming that the area had to be cleared, as the Cathedral needed to prepare for its Sunday service - a ploy that somewhat unravelled when the vicar himself gave the occupation his blessing.

In this light, the reason for the kettle becomes obvious. Excuses of maintaining public order aside, the kettle was there to disperse the occupation - a legitimate protest - entirely. But Occupy London are a tenacious group. Interviewing several tent-owners, I asked how long they were planning to stay; I always received the same answers - "as long as it takes... as long as possible".

The day wore on, and police tactics became more aggressive. By 4pm they had restricted the territory of the occupation considerably, and by 6pm the entire 'general assembly' was confined to the steps of the Cathedral. From there they forced a contingent of riot police behind the assembly, ostensibly to 'defend the Cathedral from damage'. Needless to say, there was never any sign that this was likely.

Compacting the kettle was also achieved in an important manner. I witnessed several times a sergeant circle behind the police line and roar "charge". Though the movement itself would be better described as a determined walk forwards, the distinctly military feel to this command has the desired effect. And that desired effect defines the goal of policing Occupy London: intimidation.

In his speech, Julian Assange described the Occupy movement as "a culmination of dreams". On October 15th, it was surrounded by a culmination of intimidation.

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