A few minutes later riot police wearing balaclavas and carrying Taser stun guns scaled the roof with ladders and ropes and smashed through a trapdoor into the rooms below.
Within minutes it was all over. Around 20 protesters were handcuffed, searched and questioned for two hours as part of a very public police response to Wednesday's riots at the Bank of England.
The protesters accused the police of unnecessary brutality. The police said they had intelligence that some of the residents were among the ringleaders of the City disturbances.
At another address near Liverpool Street in the east of the City of London, a large convoy of police vans arrived in the quiet back street and officers in protective clothing forced their way inside a squat.
At least 70 people were led out of the building and made to sit in the street outside as they were questioned and searched. Some were restrained with plastic handcuffs. One onlooker said a man with a head injury was taken outside and there were sounds of resistance from those inside.
But elsewhere it was mainly quiet. At the ExCeL centre protests were peaceful as various groups gathered throughout the day. The largest and most vocal protests came from two Ethiopian factions from Manchester and London who were complaining about human rights abuses in their African nation.
The two squats were raided yesterday at approximately 12.30pm, the first in Rampart Street, Whitechapel, the second off Earl Street, EC2.
The Metropolitan Police said four people were arrested in Rampart Street, two for violent disorder and two for possessing an offensive weapon.
Throughout this week's protests the squatters in Rampart Street have been advertising their building on the internet as a place where demonstrators could meet and sleep. A former Islamic school which was taken over by squatters five years ago, it is normally used as a community arts centre and is well known among left-wing activists in east London.
Those left to clear away the debris after the raid complained about what they said were overly heavy-handed tactics used by the police.
One Italian activist, who would reveal just his first name, Paulo, and was sporting a large bruise on his cheek, said: "The police stormed into the place like something out of the movies. I was punched in the face by a riot cop and then had a stun gun pointed at me. It was terrifying. If they'd knocked we'd have let them in."
Another female resident accused the police of being equally responsible for the violent confrontations. "They've been deliberately increasing tensions among protesters," she said. "A lot of fuss has been made about a few broken bank windows, but what about the police using truncheons on protesters?"
Superintendent Roger Evans, who was involved in the Earl Street raid, said intelligence officers had been watching the squats throughout the protests and were hoping to match some of the inhabitants with photographs of those who caused trouble on Wednesday.
"We have had officers keeping this building under overt surveillance," he said. "Our intelligence teams have been watching this [premises] for the last two days.
"A decision was made to see if anybody was involved in the violence yesterday. I don't know exactly how many people were inside but it's about 70 so far. There are all sorts of people inside. People with piercings, people without piercings, people with dogs – the sort of people you might expect to see at a pop festival."
The police have now released the name of the man who collapsed and died near the anti-G20 protests in the City on Wednesday.
Ian Tomlinson, 47, a City resident, was on his way home from work at a newsagent when he collapsed near the Bank of England just before 7.30pm. Police officers were reportedly pelted with debris as they tried to resuscitate him.
Until details of his death were announced late yesterday afternoon, protesters had assumed Mr Tomlinson was a fellow-demonstrator and consequently held a vigil for him.
Climber's climate change protest
French free-climber Alain Robert yesterday scaled the Lloyds tower and unfurled a large banner from the ninth floor warning that there were only 100 months left to save the world from climate change. Robert has climbed some of the world's tallest buildings without ropes, including the Petronas Towers in Kuala Lumpur and Canary Wharf. He has so far scaled around 85 giant structures around the globe. While scaling the Sears Tower in Chicago in 1999, thick fog set in, covering the glass and metal wall with moisture and making it dangerously slippery but he succeeded in reaching the top.Reuse content