Look up — who’s that pinned like a bug to the battlements of the Houses of Parliament? Is it Batwoman — or another less fanciful heroine? Emmeline Pankhurst, perhaps, or Joan of Arc? No it’s a 23-year-old called Tamsin Omond, protesting against the expansion at Heathrow by climbing the Palace of Westminster.

Omond is one of a new breed of eco-activists. Spurred on by the lack of government action in the face of immeasurable climate change, these kids are taking radical action. Among them are the usual suspects — pressure groups and stalwart eco-warriors — but also a more glamorous crew, with Omond at the helm. Young, aristocratic (she’s the granddaughter of a baronet), clever (Cambridge-educated) and very pretty, her stunt on the Houses of Parliament prompted front-page headlines about the “rooftop rebel”.

Her looks have had the likes of Vogue and Tatler (who want to photograph her on a horse dressed as Lady Godiva) beating a path to her door, while her uncompromising attitude has made her attractive to hip brands — right now, a well-known “quite cool” fashion label is trying to sign her up to be its “face”, but she won’t tell me which one it is; she doesn’t seem that bothered.

I meet her first in the rain, in a tent, on a camp site in Wales. It is a lecture weekend set up by the ethical clothes brand Howies, and she has been invited to give a talk. She’s wearing an anorak and red and white stripy cotton shorts with bare legs. She has a mop of curly blonde hair, and her eyes are caked in eyeliner. She’s sort of mad-looking, but also sort of cool, too. She’s actually a bit of a starlet.

Eventually I track her down to a cafe in Dalston, east London, near where she lives. She’s in black trousers, Converse trainers and a brown, tweedy army coat with the collar half up, and she sketches out her story for me. A privileged upbringing in Hampstead, an education at Westminster School, and on to Cambridge. The future involved an important job with a multinational, a nice big house, kids. Then came a calling to the priesthood (“To put something at the centre of my life that wasn’t me”), then a revelation. Alone in her house one day, she fell upon some climate science information left lying around by her housemates. She started reading and couldn’t stop. She put God on hold and turned her mind to the environment.

It isn’t a surprise that she wanted to be a priest, but she does make a surprising eco-warrior. For a start, she doesn’t seem like a do-gooder. She’s naughty. She says she’s less likely to be found, of an evening, eating lentil stew than in the queue for a 1990s club night, Work It, in east London. “Climate change is the only thing I’d have become an activist for,” she says. “I wouldn’t have bothered for anything else.”

Neither does she take herself too seriously. She’s just moved into a house of vegetarians, but says: “It’s a bit heavy-going. Me and a flatmate sneak out once a week to get a burger.”

And the other day she was accosted by a man who had seen her face in the paper. “He grabbed me and said, ‘You’re a climate activist! And I’ve got the answers! We need to have a permaculture garden, a worldwide permaculture garden!’ I was like, yeah, right . . .”

Of course, a giant permaculture garden isn’t going to save the world, and she’s far too smart to believe in one grand solution. She says she’s just trying to be the spark that starts everyone thinking.

In October, Omond helped organise the Climate Rush, a rally inspired by Pankhurst on the 100th anniversary of the suffragette rush on Parliament. She led a gaggle of girls dressed in Edwardian costume who handed out fairy cakes and demanded an end to airport expansion, an end to plans for coal-fired power stations and a raft of new government policies to tackle global warming. More than 1,000 people turned up, including a large contingent of concerned yummy mummies, who brought their children.

Gordon Brown might have been busy that night, but the story made the news, and the police seemed flummoxed — partly, one suspects, because everyone looked so stunning. Smart move: the march moved peacefully to the main entrance of the House of Commons, where it turned into a party with dancing.

Not that Omond got to see much of it. After leaving her MA exam in environmental science an hour early to get to the rally on time, our heroine was duly arrested for breaking the terms of her bail from her previous parliamentary protest.

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