The young woman brandishing a chopped-up sofa cushion did not look as though she was "importing a frightening brand of continental violence".

Yet that, according to a senior London policeman, is what the group she belongs to - the Wombles - is all about.

"I need a volunteer," she said. Most of the 50-strong meeting looked at the floorboards of the smoky hall.

The cushion and the overalls are the homemade protective gear of choice for anti-capitalists. She would prefer it, she said, if her volunteer were female.

"It's just to get away from all this nonsense that only men can do the frontline stuff," she said.

White overalls have become the trade mark of a growing community of European activists adopting a particular style of street protest.

Using techniques inspired by the Zapatista movement in Mexico, they aim to stand their ground in direct confrontations with police, using padding against batons and riot shields.

And - so their supporters claim - they do not resort to violence.

Boards

At the public meeting leading up to this week's Mayday protests, we learned how to make body armour from sofa cushions cut down the middle and taped to estate agents' boards - which you can "pick up in the street".

Motorbike helmets give good protection, although you can't smoke in them, someone chipped in.

And, the advice went on, carry a bandana soaked in vinegar in case the police start using CS gas.

The gathered activists obviously intended to cause some serious disruption on the streets of their target area, Mayfair, on 1 May itself.

But they also showed a strong regard for the law. This is not least because, for those venturing into the grey area between Gandhi-style sit-downs and illegal rioting likely to end in conviction, the law - in theory - provides more protection than any amount of adapted upholstery.

There was a wave of scribbling as an earnest, black-clad twenty-something explained the magic formula: "Section 3 of the Criminal Law Act 1967." This states that citizens have the right to use "reasonable force to prevent a crime taking place".

Therefore, our activist legal adviser explained, if the police are acting - or appear to be about to act - unlawfully, citizens have the right to respond with force.

Warnings

Then came the warnings. Understanding public order offences is crucial. For example, he said, one protester has been sentenced to two years in jail for throwing a water bottle at the police. The offence was classed as violent disorder, which carries a maximum penalty of five years.

The Wombles describe the increasing use of body searches, address-taking and the photographing of crowds at demonstrations as the process of the "criminalisation of dissent".

The main thing that stopped me from offering to try on the Michelin-man kit out of curiosity was a small but persistent fear that the policemen or the press photographer waiting outside the entrance to the building would walk in.

The key message was, therefore, "know your rights". You are doing nothing wrong by assembling to protest in a public place, even without police permission, we were assured.

If you are searched under "S60" - Section 60 of the Criminal Justice Act - you are being searched for weapons. This does not give the police the right to write your name and address down from your credit cards or diary, although, we were told, they have tried to do so at previous demonstrations.

In that situation they can, however, make you remove masks. But, the young man said, a recent trial suggests you might get away with sunglasses or face paint.

The tips continued. If you get arrested, give your name, it speeds things up. If you think you are being mistreated, demand the officer's number. He or she is obliged to tell you, although many police officers cover their ID numbers up, we were told.

Fed-up

The last two Mayday protests have ended in long stand-offs, with thousands of fed-up protesters held for hours in Oxford Circus last year, and Trafalgar Square the year before.

To avoid this at Wednesday's event, there is no advertised meeting point. Activists are being told to simply converge on Mayfair and keep moving.

And that was it. There was no detailed tactical planning and no one who could be described as a ringleader.

We left by the back door to avoid the policemen who were keeping watch at the front of the building. As we filed out, a group of teenage boys in front of me covered their faces and raised their middle fingers - a parting shot at the newspaper photographer parked across the road.