The first time I met Margaret Thatcher, I swear she was wearing gloves. The place was her office at the Department of Education, then in Curzon Street. Maybe my memory is fanciful. Perhaps she had just come inside.

But without any question, sitting behind her desk, she was wearing a hat. The time was 1973. This was the feminine creature who, two years later, was leader of the Conservative party. Steely, certainly. The milk snatcher reputation absorbed and lived with. Lecturing me about the comprehensive schools, of which she created more than any minister before or since. But a woman who, at the time, thought that chancellor was the top mark at which she might aim. Conscious of being a woman, and incapable of pretending otherwise. Indeed a person – with a chemistry that repelled almost all the significant males in Edward Heath's cabinet – who could never become the party leader.

Being a woman is undoubtedly one of the features, possibly the most potent, that makes her ascent to power memorable, 25 years on, in a way that applied to no man. Harold Macmillan, Alec Douglas-Home, Heath: they seem, by comparison, evanescent figures.

Thatcher is remembered for her achievements, but more for a presence, which was wrapped up with being a woman. Several strong women on the continent have risen to the top, but this British woman, in Britain of all places, became a phenomenon, first, through her gender.

The woman, however, changed. The gender remained, its artefacts deployed with calculation. But it was overlaid by the supposedly masculine virtues, sometimes more manly than the men could ever assemble. She became harder than hard. Sent Bobby Sands to an Irish hero's grave without a blink. Faced down trade union leaders after her early years – apprentice years, when Jim Callaghan's Britain was falling apart – in which the commonest fear was that the little lady would not be able to deal with them across the table.

Thatcher became a supremely self-confident leader. No gloves, or hats, except for royalty or at funerals, but feet on the table, whisky glass at hand, into the small hours of solitude, for want of male cronies in the masculine world she dominated for all her 11 years in power.

Draining down those 11 years to their memorable essence, what does one light upon? What is really left by Thatcher to history? What will not be forgotten? What, in retrospect, seems creative and what destructive? Are there, even, things we look back on with regret for their passing? Would we like her back?

I think by far her greatest virtue, in retrospect, is how little she cared if people liked her. She wanted to win, but did not put much faith in the quick smile. She needed followers, as long as they went in her frequently unpopular directions. This is a political style, an aesthetic even, that has disappeared from view. The machinery of modern political management – polls, consulting, focus groups – is deployed mainly to discover what will make a party and politician better liked, or worse, disliked. Though the Thatcher years could also be called the Saatchi years, reaching a new level of presentational sophistication in the annals of British politics, they weren't about getting the leader liked. Respected, viewed with awe, a conviction politician, but if liking came into it, that was an accident.

This is a style whose absence is much missed. It accounted for a large part of the mark Thatcher left on Britain. Her unforgettable presence, but also her policy achievements. Mobilising society, by rule of law, against the trade union bosses was undoubtedly an achievement. For the most part, it has not been undone. Selling public housing to the tenants who occupied it was another, on top of the denationalisation of industries and utilities once thought to be ineluctably and for ever in the hands of the state. Neither shift of ownership and power would have happened without a leader prepared to take risks with her life. Each now seems banal. In the prime Thatcher years they required a severity of will to carry through that would now, if called on, be wrapped in so many cycles of deluding spin as to persuade us it hadn't really happened.

These developments set a benchmark. They married the personality and belief to action. Britain was battered out of the somnolent conservatism, across a wide front of economic policies and priorities, that had held back progress and, arguably, prosperity. This is what we mean by the Thatcher revolution, imposing on Britain, for better or for worse, some of the liberalisation that the major continental economies know, 20 years later, they still need. I think on balance, it was for the better, and so, plainly did Thatcher's chief successor, Tony Blair. If a leader's record is to be measured by the willingness of the other side to decide it cannot turn back the clock, then Thatcher bulks big in history.

But this didn't come without a price. Still plumbing for the essence, we have to examine other bits of residue. Much of any leader's record is unremarkable dross, and Thatcher was no exception. But keeping the show on the road is what all of them must first attend to, because there's nobody else to do it. Under this heading, Thatcher left a dark legacy that, like her successes, has still not disappeared behind the historical horizon. Three aspects of it never completely leave my head.

The first is what changed in the temper of Britain and the British. What happened at the hands of this woman's indifference to sentiment and good sense in the early 1980s brought unnecessary calamity to the lives of several million people who lost their jobs. It led to riots that nobody needed. More insidiously, it fathered a mood of tolerated harshness. Materialistic individualism was blessed as a virtue, the driver of national success. Everything was justified as long as it made money – and this, too, is still with us.

Thatcherism failed to destroy the welfare state. The lady was too shrewd to try that, and barely succeeded in reducing the share of the national income taken by the public sector. But the sense of community evaporated. There turned out to be no such thing as society, at least in the sense we used to understand it. Whether pushing each other off the road, barging past social rivals, beating up rival soccer fans, or idolising wealth as the only measure of virtue, Brits became more unpleasant to be with. This regrettable transformation was blessed by a leader who probably did not know it was happening because she didn't care if it happened or not. But it did, and the consequences seem impossible to reverse.

Second, it's now easier to see the scale of the setback she inflicted on Britain's idea of its own future. Nations need to know the big picture of where they belong and, coinciding with the Thatcher appearance at the top, clarity had apparently broken through the clouds of historic ambivalence.

Heath took us into Europe, and a referendum in spring 1975 confirmed national approval for the move. Prime Minister Thatcher inherited a settled state of British Europeanness, in which Brussels and the [European] Community began to influence, and often determine, the British way of doing things. She added layers of her own to this intimacy, directing the creation of a single European market that surrendered important national powers to the collective.

But on the subject of Europe, Thatcher became a contradictory figure. She led Britain further into Europe, while talking us further out. Endeavouring to persuade the British into an attitude of hostility to the group with which she spent 11 years deepening their connection must take a high place in any catalogue of anti-statesmanship. This, too, we still live with.

One also can't forget what happened to the agency that made Thatcher world‑famous: the Conservative party, of which she seemed such an improbable leader. Without it, she would have been nothing. It chose her in a fit of desperation, hats and all – though it quite liked the hats. It got over a deep, instinctive hostility to women at the top of anything, and put her there. Yet her long-term effect seems to have been to destroy it. The party she led three times to electoral triumph became unelectable for a generation.

There are many reasons for this. But Thatcher was a naturally, perhaps incurably, divisive figure. It was part of her conspicuous virtue, her indifference to familiar political conventions. It came to a head over her most egregious policy failure, Europe. She lost seven cabinet ministers on the Europe question, a record that permeated the party for years afterwards. It still does. So the woman I met in Curzon Street, dimpling elegantly, can now be seen in history with an unexpected achievement to her credit. She wrecked her own party, while promoting, via many a tortuous turn, Labour's resurrection.

The last time I met her was after all this was over. We had had a strange relationship. She continued for some reason to consider me worth talking to. Yet I wrote columns of pretty unremitting hostility to most of what she did. It became obvious that, while granting that I had "convictions", she never read a word of my stuff.

For years, in fact, she despised writers, except those who did her speeches. Why don't you get a proper job, she once sneered at me. Yet, at that last encounter, her tone was different. She had just finished the first volume of her memoirs, which she insisted was all her own work. This has been a terrible labour, she said. It was all very well for me to write books. I was a professional writer. She was not a writer. It came very hard, getting the words and paragraphs in the right order, a task for which, she eventually admitted, she had hired some help.

But now the history was what mattered. Getting the record straight.

Making sure the verdict wasn't purloined by others. Everything has its season. Promises. Action. Words. Hats. Gloves. Handbag. Now it was the turn of the words, and no one, of course, would, against all the odds, do them better than the lady who, 25 years before, once thought the sky was beyond her limit.

Hugo Young was a political columnist for the Guardian from 1984 until 2003 and biographer of Margaret Thatcher. He wrote this piece in 2003, two weeks before he died.