Joan Smith: Pussycat bows? What was Maggie thinking?

On the day Margaret Thatcher was confirmed as leader of the Conservative Party, she wore a light-coloured suit with a huge silk bow at the neckline. The bow was one of her trademarks, sending a message about how she intended to tackle her new job. Thatcher might be accused of "wearing the trousers" – a common insult towards ambitious women then – in a party shocked to find itself with a female leader. But her clothes promised she wouldn't do it at the expense of her femininity.

Tomorrow, seven suits worn by Thatcher in the 1970s are to be auctioned by Christie's. The colours are surprising: pale green, peach and canary yellow, in contrast to the deep blues and maroons she favoured later. This is the uniform Thatcher adopted when first under public scrutiny – a classic example of defensive dressing, emphasising that she was middle-class and middle-aged at a time when half the country was getting into jeans.

The Conservative Party didn't know what to make of Thatcher. Neither did some reporters. "From my teens I've looked after my skin," she told a Sun journalist during the 1979 general election campaign. "I never used soap and water on it, although I come from a very soap-and-water-minded family." I don't suppose the outgoing prime minister, Jim Callaghan, had to field many questions about his cleansing routine.

When she became prime minister, Thatcher was one of only eight women on the Tory benches. Her choice of clothes aged her, but it also sat oddly with her steely ambition. France's President Mitterrand said as much, according to his aide Jacques Attali, who remembered his boss observing that Thatcher had "the eyes of Stalin and the voice of Marilyn Monroe". It's a disconcerting image, juxtaposing masculine power and feminine seductiveness. In a staunchly reactionary party, it was also a huge gamble.

Thatcher didn't promote Tory women or bother to make alliances with the handful of female MPs struggling to follow in her footsteps. Tory men never quite trusted her. She ended up isolated from both sexes, only discovering how few friends she had when she was forced to fight for her political life in the autumn of 1990. The suit she wore for her resignation speech was a sombre, funereal version of the outfits she wore in her early days.

She went out in a sober plum skirt and jacket, a female version of a man's suit. Every aspect of her voice and appearance jarred: she was brittle, constructed and artificial. After all those years, Margaret Thatcher still hadn't resolved her confusion about gender and power. And I can't think of a better symbol of it than those dreadful pussycat bows.

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