LONDON -- Margaret Thatcher's resignation has rapidly become Britain's equivalent of the Kennedy assassination, and not just because it also happened on the 22nd of November.

The news broke here about 9:30 a.m., shocking the country. It was announced over the loudspeaker on tube trains; it was shouted in the street; independent television abandoned all its programs for live news for the first time since Kennedy was shot. True to form, even the way the news spread caused controversy. At Heathrow Airport, whoever was at the loudspeaker said, "A lot of you may be pleased to hear that Margaret Thatcher has resigned." The airport authorities later apologized for this breach of objectivity.

Thatcher's fall was bloodless, but the analogy with political assassination is more than a little apt. It was sudden, ruthless and done by a cabal; and the manner of her going will enhance her historical reputation.

For Thatcher has been toppled before failure could really tarnish her, as were Kennedy and Lincoln and Julius Caesar. True, she was presiding over an inflationary recession as bad as the one she inherited when she took office in 1979. But suppose she had lost the next election and then resigned in ignominy, or struggled on until she became an embarrassment to her party and herself. It would have been quite out of character for Margaret Thatcher's extraordinary reign to have ended that way. The blazing, shocking, sudden events of last week were more her style. Only her "last words" were a little out of character: "It's a funny old world," she told the Cabinet as she announced her resignation.

Indeed it is. Like John F. Kennedy, she has never lost an election since entering politics. She never even lost an important vote in the House of Commons as prime minister. (Such losses, along with retirement, are the two ways prime ministers are supposed to go, under Britain's unwritten constitution.) Indeed, just last week, she won a contest for the leadership of her party by 14 points: 55 percent of the vote, as opposed to Michael Heseltine's 41 percent. And yet she has been stabbed in the back by that party.

Why? The irony is that although Europe was the cause, it was not the reason for her downfall. All the events that led eventually to Thatcher's resignation were disagreements over policy towards Europe. First, Heseltine walked out of her Cabinet in a rage in 1986 because he wanted a European consortium, not an American one, to buy a troubled British helicopter company. For four years, he stalked the country, building debts by making speeches for members of Parliament in their districts. Second, Nigel Lawson walked out of her Cabinet in a rage in 1989 because he wanted the pound to join the European Exchange Rate Mechanism and she did not. Third, Nicholas Ridley, her closest ally on Europe, had to resign from her Cabinet in 1990 because he had insulted the European commission and the Germans. Fourth, and fatally, last month Sir Geoffrey Howe, the only remaining member of her very first Cabinet, walked out of the current Cabinet in a rage over her intransigence towards European monetary policy. Howe's vicious speech after his resignation led to Heseltine's challenge for the leadership, which led to her resignation. So Europe was the cause.

Yet the reason she resigned was not that a series of her senior ministers attacked her policy towards Europe. The reason she resigned was that 152 members of Parliament in her own party voted for Heseltine and not her last Tuesday. And very few of them did that because of Europe. They did that because they didn't want to lose their seats at the next election. They read the opinion polls, in which Thatcher has long been less popular than her party, and where her party has been trailing Labor for the last 18 months. They read the opinion polls which hinted that a Heseltine-led party would win where a Thatcher-led party would not. They saw the effect of the dreaded poll tax on the fortunes of Tory candidates in by-elections. They got rid of her not because they disagreed with her, but because she was unpopular. Seen from Europe, however, Thatcher will seem to be merely the most famous casualty of defying the British people's yearning for continental unity. Jacques Delors and Helmut Kohl, her principal sparring partners on the continent, will probably see it that way. Certainly, she could have accepted their proposals for economic and monetary union, plus a European central bank, without losing popularity at home. The sort of mystical belief in the pound and the undiluted sovereignty of Parliament over economic policy that she says she has been defending is not something most British people care a fig about. In any case, monetary union would not happen until the late 1990s, by which time the problem would surely have been someone else's.

So why did she oppose it so fiercely? The real reason seems ironic, given what she set out in 1979 to achieve. She has become convinced that Britain would end up under the thumb of the Deutsche mark, disciplined by interest rates set by a European central bank and unable to devalue its currency or inflate its way out of trouble. Britain's inherently low productivity would show up in slower growth and higher unemployment.

The argument is logical enough. But it is astonishingly defeatist for a woman who came to power determined to reverse Britain's relative decline and not merely accept that Britain must lag behind other countries, for a woman who presided over a manufacturing productivity growth rate of 4 percent a year (exactly twice the German rate of productivity growth over the same period), who brought unemployment down well below the German rate, and in whose time British economic growth and labor-force growth comfortably outpaced Germany's. It is ironic indeed for a woman whose addiction to stern anti-inflationary measures led her to deflate the economy with tax increases in the depths of a recession, when unemployment was 8 percent and rising fast.

It is all history now. All three of those who would succeed her are in different measure enthusiastic Europeans. They might drag their feet a little over monetary union when it gets closer; they might protest, as she did, at Jacques Delors's plan to turn the European Parliament into Europe's legislature and the European Commission into its executive. But they will be a lot less trouble for Delors than she would have been. That matters not very much to the self-preservationist Tory MPs who voted against her. What matters to them is that they will have a leader who does not have the albatross of the poll tax around his neck going into the next election.

It was about the most cold-blooded affair in British politics since King Charles was decapitated. "Monstrous cruel," said the Times the next day and filled its letters column with the reactions of shocked Britons: "Donkeys led by a lion," wrote one; a "triumph for naked, shallow opportunism," said another; a third suggested that dictionaries should now cite the phrase "the Tory faithful" as an example of the meaning of the word "oxymoron".

It was only a few hourse after her decision that the enormity of what they had done dawned on these MPs. Neil Kinnock had called a vote of confidence in the government on the day Thatcher resigned, and she made the speech of her life in opposing it. It was fierce, hard, partisan stuff, filled with statistics justifying her record, bellowed out in that trade-mark bass voice. At one point, she paused and cried, "I'm rather enjoying this!"

I was in a taxi at the time and we screeched to a halt. The driver simply could not contain his laughter. "You know", he said, "I bet those MPs are regretting what they've done. I'm no supporter of hers, but she didn't deserve this."

The ironies abound. Such was the sympathy for her on Thursday that in the hour of her nadir, she was probably suddenly as popular as she had ever been. Of all Britain's postwar prime ministers, she had, on average during her term, the second-lowest approval rating (40 percent; only Heath's was lower). It never rose above 55 percent, even just after the Falklands War. And by resigning she may indeed have saved the party at next election: the Conservatives, under whomever they choose, are already ahead of Labor in the polls again. More than that, she may have saved the party from what she saw as an even worse fate: Michael Heseltine. To make him prime minister now would be almost like making Brutus dictator of Rome.

Matt Ridley is editor of The Economist's American Survey section.