A man dressed as Spiderman whose vigil for fathers' rights atop a 150ft crane triggered traffic chaos was today cleared of causing a public nuisance.

David Chick, who blamed the police for the "unnecessary" disruption that cost businesses an estimated £50m, staged his stunt on a building site near London's Tower Bridge. He was protesting being refused access to his four-year-old daughter.

Police officers, who claimed that he could have fallen fall on pedestrians or cars, promptly halted work on a £45 million office block development and sealed off the surrounding streets.

That rapidly brought gridlock to swathes of the City and east London, with frequent ten-mile traffic jams.

The former window cleaner, who is said to hate heights, refused repeated requests to come down as drivers fumed, workers rang in late and police costs spiralled by £10,000 a day.

Prosecutor Anthony Wilkin had branded the defendant a "maverick" who presented an "unacceptable risk, a danger to the public, an unknown threat" that could not be ignored.

But Mr Chick, a veteran of three similar crane-top protests, insisted that the police had been responsible for the disruption during his latest stunt.

During his trial Mr Chick accused the police of playing a "psychological game" in a bid to make him look like a "reckless idiot" and "turn the public against me".

"The police and the authorities chose to disrupt so many people's lives, which was totally unnecessary," he added.

The jury of five men and seven women at Southwark Crown Court also heard excerpts from police logs making it clear that senior officers not only treated the road closures as a "bargaining tool" to get him to come down, but also worried that the court case against him could be "weakened" if they were lifted.

As the not guilty verdict was announced, Mr Chick grinned broadly while around 20 supporters – mostly men wearing Fathers4Justice t-shirts – cheered and applauded.

Outside court the clearly delighted 37-year-old, who lives with his mother in Burgess Hill, west Sussex, pulled on a Spiderman mask and indulged in several changes of t-shirt. One read: "Police spin version exposed", while another declared: "Family law fails children and dads."

Asked for his reaction he said: "Common-sense verdict."

When someone asked whether he intended to stage another protest his response was equally brief: "Watch this space."

The nine-day trial heard that the father of one and his former partner – who cannot be named for legal reasons – set up a cleaning business and had a daughter during their three-year relationship. But ten months after she was born they separated.

Mr Chick told the jury that despite a subsequent court order allowing him to visit his daughter for two hours every week, the child's mother was less than willing to allow him access and eventually refused altogether.

Increasingly unimpressed by the legal system, he decided to take matters into his own hands and felt that crane-top protests offered the best prospect of drawing attention to his difficulties.

Mr Chick staged 48-hour protests on top of cranes in Victoria in London, Guildford, Surrey and St Katherine's Way near Tower Bridge, but was never charged.

Then, Mr Chick was given a three-month home curfew order after being convicted for harassing his former partner. Just hours after the curfew expired, he returned to St Katherine's Way and climbed a different crane.

Once at the top with eight litres of water, some food, a blanket, toothbrush and "my old granddad's pocket knife," he donned his Spiderman outfit – his daughter's favourite superhero.