Twenty squatters were being questioned by police today after a string of raids on the eve of the royal wedding.
Scotland Yard swooped on three addresses across London after an intelligence-led operation was brought forward ahead of the big day.
Police said the arrests were not "specifically related" to the wedding despite an MP criticising the "disproportionate" operation as "some form of pre-emptive strike".
The three warrants were carried out as part of "ongoing proactive work to tackle suspected criminality", police said.
One person was arrested in Hackney, east London, in connection with disruption at the TUC march while the other 19 were arrested in Camberwell, south London, for abstracting electricity, a Metropolitan Police statement said.
Another raid was carried out on a squat occupied by the Transition Heathrow campaign group in Sipson during the dawn operations.
The raids came after police said they would carry out a number of arrests ahead of the most expensive and high-profile security operation in a generation.
Occupants at the addresses in Camberwell and Heathrow said they were angry at being targeted by police.
Joe Rake, 20, a Transition Heathrow campaigner, said he woke up to 40 officers raiding the property at dawn.
"They asked us if we had been involved in the TUC protests," he said.
"It seems obvious to us that they thought we were going to do something at the wedding tomorrow.
"They searched through our things but took nothing away and made no arrests."
A man affiliated with the squats on Camberwell Road said people living with him ran a bicycle workshop for the community, were not political and had no view on the wedding.
Another squatter said: "The idea that the anarchist community or squatting community is mobilising for the royal wedding is insane.
"I think the real motive for this is to lead an assault on the squatting community.
"It's political policing which is designed to be theatrical and which damages people's lives in the process."
Labour backbencher John McDonnell raised a point of order in the Commons to question whether the raids were necessary.
He said: "I believe this disproportionate use of force is unacceptable and I would urge that a minister comes to this House from the Home Office to explain what is exactly happening today, what are the grounds for that action and also to contact the Metropolitan Police Commissioner to explain that many of us feel that this is disproportionate and no way to celebrate this joyous wedding."
More than 5,000 officers will make up a multimillion-pound ring of steel tomorrow as the world's attention focuses on London.
Snipers will take to rooftops and undercover officers will mingle among the crowds as part of a massive covert and overt operation to avoid an atrocity.
Security against potential threats from al Qaida-inspired extremists, dissident Irish republican terrorists, anarchists and even lone stalkers is being balanced with the desire to let onlookers enjoy the day of pageantry.
Around 70 people are now banned from the City of Westminster as part of their bail conditions after being arrested or charged over various previous alleged disorder offences.
But with up to 80 VIPs requiring personal protection, no intelligence has suggested police need to use anti-terror powers as hundreds of thousands arrive in the capital for the event.
Police have been scouring London for explosives and hidden weapons in recent days, inspecting drains, lamp-posts and traffic lights in Westminster.
In total, three protest groups formally declared intentions to cause disruption but Muslims Against Crusades announced yesterday that it had abandoned plans amid fears that protesters could become a target.
The English Defence League is now thought unlikely to be planning any action.
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