Police threw a section 60 cordon around the whole of the royal wedding zone on Friday morning to respond to anarchists masking up at a small gathering in Soho Square in central London.

The section 60 order allows police officers to stop and search anyone without discretion. The police also imposed section 60a, which gives them the power to remove masks and balaclavas from anyone within the area.

Scotland Yard said the decision was made after individuals were seen putting on masks in Soho Square where a group of anarchists had gathered.

At least one arrest was made after a clash in the square between plainclothes officers and one individual after he started singing "We all live in a fascist regime" to the tune of We All Live In a Yellow Submarine.

By 12.45pm police said 43 arrests had been made across the royal wedding exclusion zone. These included one for criminal damage.

The arrests took place in and just outside the exclusion zone around Westminster Abbey and Buckingham Palace.

Scotland Yard said two people were arrested for being drunk and disorderly, one for assault, one for possessing an offensive weapon, two for breach of the peace, two for theft.

The biggest security operation in the Metropolitan police's recent history has seen the deployment of 5,000 officers, including a 1,000-strong rapid-response team to react to any criminality, direct action or extremist threats inside and outside the exclusion zone.

In pre-emptive action on Wednesday and Thursday officers from the Metropolitan police raided five squats in London and one in Hove, arresting 21 people.

All were released and bailed with conditions that bar them from the City of Westminster on Friday.

On Thursday night Cambridgeshire police arrested Charlie Veitch, a self-confessed anarchist, for conspiracy to cause a public nuisance and breach of the peace.

It is understood police believed Veitch, who runs a group called Love Police, was planning to cause disruption in Soho Square. His girlfriend, Silkie Carlo, told the Guardian Veitch was planning to use a megaphone to make "ironic comments" in the square.

Speaking about the arrest, Carlo, 21, said: "Charlie was arrested around 5pm from our home on suspicion to cause to public nuisance a day before he went anywhere.

"There were two police officers and they did a brief search of our room. We were happy for them to do that. We had nothing to hide, " said Carlo, who studies politics and psychology at Cambridge University.

"Then they put Charlie in the back of a van and took him off to Parkside police station in Cambridge. He's since been picked up at 10am and taken by the Met. We don't yet know where he is," she said.

"I'm outraged. It's easy to hide all this behind the beauty and the spectacle and the tiaras of the wedding but when people with opposing political ideas are being rounded up to keep them away from public view, it doesn't make us any different from China."

Sir Paul Stephenson, the Scotland Yard commissioner, said his force was prepared for every eventuality.