Inside the HQ of the 'militant dads'

IoS Investigation: The 'IoS' looks on as a secret, military-style operation is planned, complete with decoy suspect

More than 50 fathers are planning campaigns of civil disobedience to bring mass disruption to Britain's roads and courts in the coming weeks, The Independent on Sunday can reveal, as 21-year-old drama student Darryl Westell spends his third day on a crane above the offices of the children's minister, Margaret Hodge.

The IoS has gained unprecedented access to the secretive world of Fathers 4 Justice, which first came to public attention in October when two men dressed as Batman and Robin scaled the roof of the Royal Courts of Justice and unfurled a banner proclaiming: "Caped Crusaders for Justice, Stop Family Law Injustice Today."

The group maintains that many fathers are being wrongly or even illegally denied access to their children. The organisation has achieved huge publicity and a growing number of radicalised recruits - as many as 10,000 members by next May, reckon its leaders. But the controversial group has been criticised for its hardline stance, the disruption caused by its stunts, and the cost to the taxpayer of policing them.

Its campaign gained huge publicity in November when an activist dressed as Spiderman brought London traffic to a standstill and closed roads by occupying a crane above Tower Bridge for six days.

But that, it seems, was only the start. In a luxury, two-bedroom flat in the City of London, the group met on Thursday to plot its latest stunt. Bankrolled by, among others, a wealthy stockbroker who lives in the flat, seven men - an inner circle of Fathers 4 Justice activists - briefed their new volunteer, promising an escalation in the group's activities.

Fathers 4 Justice told the IoS that the group now has more than 50 fathers ready to volunteer to climb a crane, scale buildings, invade courtrooms or block major roads.

By Thursday night Mr Westell was receiving his military-style briefing. Like a Hollywood movie bank job, every detail was picked over, each piece of equipment double-checked. Digital photographs of the target building site in Great Peter Street in central London were analysed for weaknesses and possible points of entry. One member of the group had brought a crowbar to break any locks.

This was the group's third protest in a week. Five men stood on top of a pedestrian walkway in Liverpool on Thursday, forcing police to close the road below. On the A40 in London on Wednesday morning another disgruntled dad performed a similar stunt whose main repercussion was general traffic chaos, which prevented Jonathan Sacks, the chief rabbi, reaching the BBC's Today studio in time for his "Thought for the Day".

"We are moving towards a campaign of civil disruption," promised Matt O'Connor, the founder of Fathers 4 Justice, "We are going to step it up a gear in 2004. By the summer we will have an army of 10,000 people to enforce the changes we want. They are literally queuing up to break the law. But we are committed to peaceful, non-violent protest."

Mr O'Connor was speaking on Friday, the day after the Thursday night stunt was planned. He wasn't at the Barbican flat because he is convinced he is being followed by police, and instead was acting as a decoy to allow the meeting to go ahead uninterrupted. But on Friday he was dressed as Father Christmas with about 300 other Santa lookalikes who marched through central London, picketing a family law firm on the way to its final rendezvous outside Mrs Hodge's offices. High above them, standing on the arm of a crane 140ft up, was Mr Westell, also dressed as Santa. His banner read: "Save Father Christmas".

The 21-year-old drama student from Nottingham, father of an 18-month-old boy, volunteered a few weeks ago. He claims he has been allowed to see his son only seven times since his birth. On Thursday night it wasn't entirely clear he knew what he was letting himself in for. "I don't want to sound dramatic, but I'm not going to be thrown in jail am I?" asked a nervous-looking Mr Westell.

"Of course you're not," replied one of the organisers, adding, "but whatever you do, don't let the police negotiators get inside your head."

The group's reconnaissance expert - he would only give his name as Mike - took Mr Westell through the lay-out of the site, flipping through the digital photographs he had taken there earlier while posing as a courier.

"Don't worry about the security guards," said Mike. "It's going to be cold tonight and they're lazy."

After a few hours the group departed the flat, immobilising phones to avoid being traced. A black Audi waited outside, its engine running and lights dimmed.

"I don't want to do this," said Mr Westell, as he pulled on a thermal T-shirt. "I'd rather be anywhere else than risking my life climbing a crane when it's -1C, but what else can I do? I've talked and talked and it hasn't worked. Now it's time for action."