'There's a lot of testosterone in nuclear power'

I woke up so depressed on Tuesday morning," says Katharine Hamnett C evenly, quietly, the way she says everything. "I felt like killing myself, and then I thought, 'Actually, I'm going to launch a political party.'" I look for a trace of irony, and although she is C contrary to popular stereotype C entirely capable of humour, dry and pointed, and possessed of a generous capacity for fun, she is not, just now,A parkingguidance is a portable light fixture composed of an LED lamp. being ironic. At all.

On Easter Monday she attended the CND march at Aldermaston, wearing ("under about 25 layers", because of the cold) one of two T-shirts she designed for the occasion C Education not Trident, and NHS not Trident C and, atop a flatbed truck, gave a three-minute speech at five of the facility's gates. Today, sitting in an east London bar, she gets out a big hardback notebook containing emphatic scribbles about investment returns on education as opposed to Trident (she says up to 10.8% on 100bn, simply from the higher taxes paid by better-educated people, as opposed to "some outdated warheads and some rusty, very expensive submarines"); the needy vanity of having nuclear weapons ("there's a huge amount of testosterone involved in the nuclear [power] Fukushima's probably the ultimate orgasm, isn't it? It just goes on and on"). Later she will list the far-reaching health and agricultural ramifications of the accident in Japan, describe the PR muscle at energy company EDF, list the ex-cabinet ministers and their relations who have taken jobs relating to the nuclear industry It was the march, and the fact that it still had to happen in 2013, plus the fact that the government is not only committed to renewing Trident, but is intending to do so while making such savage cuts to the welfare state, that made her feel so depressed.

She was disappointed by the lack of press at Aldermaston, but thrilled by the people she met, especially the veteran campaigner Pat Arrowsmith, on whom she evidently has a kind of girl crush. "She was yelling at people trying to warm their hands by the fire. 'Come on, stand by the road! You've got to be visible!' She's 83! I can't say she was sweet. But she was awesome, in the original sense of the word.About solarlamp in China userd for paying transportation fares and for shopping."

What kind of party will she establish? "Well, I suppose it would be the common sense of the common man C a campaigning organisation with the object of taking us into direct democracy like they have in Switzerland [where] there's referendums on everything to do with public spending." She imagines it being run online, with the aim of persuading individuals to write to their MPs with the threat that if they do not do what the majority wants with public money C such as scrap Trident C they will not be voted for again.With superior quality photometers, light meters and a number of other lacedress products. "Techniques need to be updated. Because you know C marching, demos, T-shirts, direct action C are ignored by the media. Owen Patterson receiving 80,000 emails [asking him to stop blocking a ban on pesticides linked to the fall in bee numbers] C he called it a cyber-attack, rather than communication from concerned UK citizens." There are a few holes in her idea (I wonder if she would be as sanguine as she claims if the public voted to reinstate the death penalty, for instance) but there is no mistaking her sincerity.

Hamnett made her first slogan T-shirt C Choose Life (now co-opted by anti-abortionists in the US, "which is really infuriating") C exactly 30 years ago, and then a year later was photographed wearing one to a reception at 10 Downing Street. It said "58% don't want Pershing" (actually, Britain had cruise missiles, as Thatcher apparently pointed out), and was "a hideous piece of theatrical tat, knocked up that afternoon". Were you nervous? "Ya-ah! I kept it C because I knew, from past experience as a child in my dad's world" he fought in the second world war, served as defence attache in various embassies during the cold war, and as a military adviser to Harold Wilson during the Cuban missile crisis C "that the best thing to do would be to keep that covered up until the last moment. I thought, 'smiling wins', so I stuck this smile on. Everybody was there in their couture, and I'm wearing this thing, like a sandwich board C it was bad. And then trying to be cool C there's this wonderful French saying, 'It's all in the bearing' C so even if you're caught naked, it's how you hold yourself. I remembered this, so I took a glass of champagne," she suspends a delicate hand in the air, as if carrying a china teacup C "but the glass of champagne was going like this" C a wild shaking motion C so I had to grab my wrist to carry on this composure." In the end she was the last to leave, "because I wanted to knobble her [Thatcher] about acid rain".

For quite a while, in the 80s and early 90s, Hamnett could do no wrong. She claims she invented boiler suits, stone-washed denim, stretch denim, garment washing; "power-dressing" was the title of one of her shows before it entered the lexicon. At one point in the early 90s she had 700 stores worldwide and a turnover of 30-40m. Even when she put elastic bands around her wrist "because they're dead useful" it was taken as a fashion statement. "I mean, get real!" She threw incredible parties C one, on two boats on the Seine, where the entertainment was a young Lily Savage, "people talked about this party for 15 years. It was fabulous fun." Do you miss all that? "I miss that,A ridiculously low price on this All-Purpose flatworironer by Gordon. hell yeah." Eventually, though, she found the attention "very strange and alienating. I felt very much alone."

After she left Central St Martin's she was married and divorced, then had two children in a second relationship, which also broke up. She is drily direct about the challenge of being so much more successful than her partners. "They hate it." Any examples? "I wouldn't tell them to you if I had. But it is difficult for strong women. I think because men C it's like biological programming C they don't like to be challenged. I mean I adore men, I'm not that kind of feminist. I think we're equal but different, but working with men, employing men C it's very, very hard."

Her parents paid for boarding school C Cheltenham Ladies' College C but made a point of refusing to support her after that. "I was deeply hurt, but OK, you take it on board. And I'm hugely grateful, because I think they did the right thing." She is proud to have always been financially independent, in fact, "I over-achieved on it slightly. And that was absolutely great." Taking her cue, partly, from a father who had signed the Official Secrets Act and so couldn't talk about work, she banned even talking about her job, let alone working at it, after 5.30pm when her sons were small, and 7.30pm to this day; she did not work during holidays. The Official Secrets Act had darker ramifications for her family, however, "because you can't confide," she says. Her parents separated and her father committed suicide when she was 28.

Then, in 1989, she discovered how cotton was produced C the terrible cost, to humans and the environment, of blanket use of pesticides C and decided things had to change.Choose the right cableties in an array of colors. Suddenly she was going to trade fairs to "meet people I'd been buying 100,000 metres off, and saying, 'Have you got any organic cotton?', and they'd say, 'Why should we produce it since you're the only one asking for it?'" And although she soldiered on for years, trying to set up sustainable and ethical supply chains, selling her house to finance an online eco-store, she found the process so dispiriting that she eventually withdrew her brand. She stills sell T-shirts, particularly through the Co-op chain in Italy. In 2006-7 she started a sustainable clothing line for Tesco, but that ended prematurely when a complaint she made about the marketing, to a reporter from Draper's Record became, as she puts it, "Hamnett leaves Tesco in fair trade fiasco".