Next week it will be 20 years since Margaret Thatcher fell. Pressure had been building on a number of fronts, but the issue that finally destroyed the former British prime minister was the yet-to-be-born euro.

In the last weekend of October 1990, she travelled to a European summit in Rome, where European Commission president Jacques Delors' dream of European Monetary Union was high on the agenda.

But while Mrs. Thatcher was fighting her lone battle against the prospective single currency abroad, she was being fatally undermined at home. Geoffrey Howe, her bitterest Cabinet critic, went on television to say that in principle Britain did not oppose the euro.

In her Commons statement after returning home, she was forced to slap Mr. Howe down: "This government believes in the pound sterling." He resigned, and days later delivered the famous speech from the back benches that set in motion a leadership contest.

Today, Margaret Thatcher's autobiography, published in 1993, reads like a prophecy. It shows how deeply and with what extraordinary wisdom she had examined Mr. Delors' proposals for the single currency. Her overriding objection was not ill-considered or xenophobic, as subsequent critics have repeatedly claimed.

They were economic. Right back in 1990, Mrs. Thatcher foresaw with painful clarity the devastation it was bound to cause. Her autobiography records how she warned John Major, her euro-friendly chancellor of the exchequer, that the single currency could not accommodate both industrial powerhouses such as Germany and smaller countries such as Greece. Germany, forecast Mrs. Thatcher, would be phobic about inflation, while the euro would prove fatal to the poorer countries because it would "devastate their inefficient economies".

It is as if, all those years ago, the prime minister possessed a crystal ball that enabled her to foresee the catastrophic events of the past year or so in Ireland, Greece and Portugal. Indeed, it is one of the tragedies of European history that the world chose not to believe her. President Mitterrand of France and chancellor Kohl of Germany dismissed her words of caution. And when Mrs. Thatcher was driven from office in 1990, a crucial voice was lost, and a new consensus started to form in Britain in favour of the euro.

This consensus stretched across the entire spectrum of the British establishment. It took in Tony Blair's New Labour and all of Paddy Ashdown's Liberal Democrats. The CBI came out for the euro, and so did the trade unions. The Foreign Office was doctrinally pro-single currency. Leading businessmen, such as Peter Sutherland (chairman of BP and Goldman Sachs International) and the fashion-conscious Richard Branson were strongly in favour. The Financial Times was another supporter.

This consensus was all the more powerful because it contained Conservative grandees. The Britain in Europe campaign, featuring an ambitious young Liberal Democrat called Danny Alexander, now the chief secretary to the Treasury, was launched in 1999. Tories Ken Clarke and Michael Heseltine treacherously spoke alongside Labour's Tony Blair and Peter Mandelson.

"The price we would pay," announced Mr. Mandelson, "in lost investment and jobs in Britain would be incalculable." He projected that "outside the euro, there is little we can do to protect industry against destabilizing swings in the value of sterling." Michael Heseltine spoke apocalyptically about the terrifying consequences for British competitiveness outside the euro. Chris Huhne, now a Lib Dem Cabinet minister, was scathing about eurosceptics who warned that entry to the euro would cause the Irish economy to overheat -- warnings that proved to be all too accurate.

Irishman Niall Fitzgerald, chairman of the industrial giant Unilever, forecast British economic obliteration outside the euro. In a dark irony, it is his native country that now faces obliteration.

Those who challenged this consensus were ridiculed. Even Conservative William Hague, then leader of the opposition, received this contemptuous treatment. He made a series of speeches which, reread today, rival Margaret Thatcher's in their prescience. He predicted that membership would "lead to huge booms and deep recessions." Mr. Hague chillingly added that "the single currency is irreversible. One could find oneself trapped in the economic equivalent of a burning building with no exits." He noted that euro membership could lead to a "full-blown banking and financial crisis."

Nobody listened, many mocked, and Mr. Hague was accused of dragging the Tory party to the Right. The BBC, an integral part of the pro-European alliance, played its full role in marginalizing critics such as Mr. Hague. The state-owned national broadcaster lumped the Tory leader in with cranks and xenophobes. By contrast, euro supporters were invariably presented as mainstream and sensible.

But it is Mr. Hague's speeches and Mrs. Thatcher's predictions that have stood the test of time, while the excitable expostulations of Messrs. Heseltine, Blair, Mandelson and Clarke all look ridiculous today.

One other point. Margaret Thatcher may have been the first victim of the single currency, but there have been many more since: the millions who have lost their jobs and the nations that are being stripped (as she forecast) of their pride and independence. Baroness Thatcher has often been accused by her politically motivated enemies of callousness. But backers of the European project are today happy to countenance unlimited human suffering in their mission to enforce economic and monetary union. Mrs. Thatcher knew this would be the result of their deranged plan, which is why she fought to stop it. Her last battle as prime minister could not have been fought in a greater or more compassionate cause.