I wanted to put a really large message on T-shirts that could be read from 20 or 30ft away," she says now. "Slogans work on so many different levels; they're almost subliminal. They're also a way of people aligning themselves to a cause. They're tribal. Wearing one is like branding yourself." So if you plan to get something off your chest, what's the best way to go about it? The last word must surely go to Hamnett. "A successful T-shirt has to make you think but then, crucially, you have to act," she says. "What's tragic is that most of these messages [from the 80s] are still relevant today. These problems - nuclear weapons, world poverty and famine - are still around". Her Pershing T-shirt was "a bit of a practical joke, really. I'd been invited to No 10 and didn't want to go, but I realised it was a photo opportunity and I should grab it. That T-shirt gave me a voice." Hamnett's designs were copied all over the world. Wham! wore a T-shirt with the slogan "Number One" - and later "Choose Life"; Frankie Goes to Hollywood had "Frankie Says Relax". Hamnett's T-shirts became cultural signposts to the times we lived in. The slogan's most recent catwalk incarnation came via Henry Holland. In 2006, he produced a series of tongue-in-cheek T-shirts aimed at the fashion industry: "Do Me Daily Christopher Bailey", "Cause Me Pain Hedi Slimane" and "Get Your Freak On Giles Deacon". They were modelled by his friend Agyness Deyn and worn by fellow designers Gareth Pugh and Deacon when they took their catwalk bows. High-street stores from Topshop to New Look rushed to produce copy-cat versions.

In the 80s, slogan T-shirts reached saturation point because of one woman: Katharine Hamnett. Dressed in a "58% Don't Want Pershing" T-shirt, she was photographed shaking hands with the then prime minister Margaret Thatcher at a Downing Street reception for London fashion week designers in 1984. (The slogan referred to public opposition to the basing of US Pershing missiles in the UK at the tail end of the cold war.)

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