Berry, a Green Party campaigns co-ordinator who works at Imperial College, launched the Alliance Against Urban 4x4s in 2004. It has slapped 120,000 yellow and black fake parking tickets on offending vehicles. “We give out clear guidelines not to stick them on or put them on moving vehicles — and to avoid muddy ones as they might belong to farmers. People hate their cars being touched and if we do any damage, we’ll be sued.

“Doing stuff like deflating tyres, which is popular in France, is not our style; it alienates people and we wouldn’t want to be associated with the kind of radical groups that damage property,” she says.

Berry and her fellow urban guerrillas do, however, get involved in plenty of dressing up. “It’s all quite light-hearted; we come as lollipop ladies and teachers wearing gaps and gowns, and hand out school reports to the naughty vehicles. Sometimes even the owners have a giggle with us.

“There are always the ones who call us a bunch of lentil-munching hippies,” she admits. “As the group gets bigger there are plenty of people who can’t stand the idea of being an eco-warrior. They join because they are fed up with antisocial 4x4 drivers who hog the road, dazzle other drivers with their headlights and intimidate pedestrians.

“When there was a protest against Jeremy Clarkson receiving an Oxford degree, we put details of it on an e-mail; several people unsubscribed as a result. We couldn’t believe people hated 4x4s but loved Clarkson.”

According to Berry, incentives are the way forward: “There should not only be a higher road tax for vehicles with big engines and high emissions but lower tax for cleaner cars.

“We’re about to release a report contradicting Transport for London’s belief that a congestion charge for large vehicles is impossible to implement. We show that it can be applied according to carbon dioxide emissions alone, which would hit big cars as well as 4x4s.”

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