Six people were arrested under section 132 of the Serious Organised Crime and Police Bill (SOCPB), participation or organisation of an unauthorised protest.

At midday up to 200 demonstrators gathered on Parliament Square green, opposite the Houses of Parliament, for the Mass Act of Defiance.

There was a large visible police presence before the demonstration had started. Up to 15 police vans encircled the square, some filled with officers waiting for possible trouble.

Police officers patrolled the square, using stop and search orders to get the names and addresses of anyone who could be a possible protestor.

Police photographic FIT teams catalogued the protestors and journalists attending the event.

One freelance photojournalist gave out his business cards: “Just in case they arrest me, then you know who I am."

Several protestors brought banners. One said: “Defend right to protest.”

Another said: “Exercising our human right to freedom of peaceful assembly makes us criminals.”

As police issued notices of an unauthorised demonstration, an unexpected visit from the Clandestine Insurgent Rebel Clown Army caused considerable interest and laughter. The clowns (CIRCA) had not been seen since the anti-G8 protests in Scotland a month earlier.

Nervous police filmed and took notes on the clowns, then issued them with SOCPB leaflets.

“I can’t read it, its upside down,” said one of the male clowns.

They then pulled out a toy eagle and dropped it on the floor: “It’s ill,” said a clown: “It’s an ill eagle.”

“An ill eagle protest,” added another clown.

Twenty minutes after the SOCPB leaflets were distributed to protestors the police moved in.

A group of twenty officers, backed up by one FIT squad, targeted the first placard carriers.

The protestors were asked to stop their demonstration and when they refused they were then arrested.

Crowds gathered around the arresting officers chanting: “Shame on you.”

Police surrounded each arrest in a tactic known as “C Section” where they block anyone from getting too close to the arresting officers.

“It’s my human right to protest,” yelled the first protestor as she was taken away to a waiting police van.

One woman dropped to the floor as police arrested her. Officers pulled her to her feet and put her hand in a lock.

“You’re hurting her,” screamed another protestor, as a solid wall of officers pulled the arrested woman towards another waiting police van.

“It’s madness,” said one woman: “How can you go and kill so many thousands of people [in Iraq] and yet you refuse freedom and democracy here?”

“I can not comment about that,” said one officer.

Within 15 minutes six protestors had been arrested, police targeting anyone carrying a banner.

One protestor in a white cowboy hat called on others to follow him to the river Thames to dump teabags in a anti-tax re-enactment of the Boston Tea Party.

The demonstration ended with a mass sit-down. Protestors chanted: “Protest by right.”

This single peaceful action immediately drew in a substantial number of police officers, but all ended with cheering protestors and no further arrests.

One clown member was held under stop and search laws, but was soon released when the only weapon found on him was a multicoloured tickling stick.