Moments that made the year: Earthquake in Enfield: the night Middle England turned red

No other election, in recent memory, has so quickly spawned its own folklore. Were you still up for Portillo? demanded the title of one book. To miss the defining moment when the then defence secretary knew he had been rejected by the electors of Enfield North was to be left woefully out of a rare collective experience, like failing to see a winning goal at a FA Cup Final, only much, much worse. Portillo made an unusually graceful speech after the count. But that wasn't the point.

His defeat at super-Tory Enfield North - even for those not gleefully celebrating his demise as a Thatcher heir-apparent - dramatised, as no other result could have done, a landslide on a scale unimaginable when the polls had closed a few hours earlier. It was a few minutes after the Enfield count that, flushed with excitement and scarcely able to absorb the seismic nature of the results across the country, the Blairite intellectual Geoff Mulgan, now on the Downing Street staff, could think of only three words to stammer as he left a BBC party: "This is weird."

He was massively understating the case. The scale of the victory was all the more mysterious because it had, in the end, nothing to do with the previous month's frantic campaigning. The widespread perception among commentators that Labour had fought a brilliantly successful election campaign was shared by the voting public. Thirty-six per cent of voters thought that Labour had fought the most effective campaign, compared with only 11 per cent for the Conservatives, and 13 per cent for the Liberal Democrats. Judged by measurable results this was nonsense. The most striking effect of four weeks of intense electoral activity was precisely the opposite: an actual reduction in Labour's poll lead over the Tories from an impossible 25 points to a still scarcely credible 13.

The roots of those results on that extraordinary night went much, much further back than the campaign itself. Dick Crossman remarked a generation ago that "an election is the end of a long process". The implosion of British Conservatism isn't easy to summarise. The ERM catastrophe had inflicted irreparable damage on the credibility of the John Major government, as the 1967 devaluation had on Wilson's. Privatisation had proved an incontestable success in making efficient the lumbering state industries it replaced. But it also created a hugely enriched super-class, which the public was far less ready to accept.

The electorate wasn't, in the end, prepared to give the credit for an economic recovery to a government which had refused to take the blame for a recession. It was unforgiving about sleaze (drawing an infinitely more sophisticated distinction than the tabloid press had done between financial misdemeanours and sexual heterodoxy). And above all it was repelled by a party ideologically at war with itself, especially on Europe.

But it was still an election won as well as lost. As David Butler and Denis Kavanagh summarised this epochal event in the closing words of their authoritative Nuffield College Study: "The Conservatives, 18 years in power, provided the opportunity. Labour seized it." That Labour was able to do so was Blair's supreme achievement in opposition. While Neil Kinnock had heroically eliminated the poisonous legacy of the early-Eighties, unscrambling the electorally hopeless positions on Europe, defence and internal democracy, and restored to Labour some of the respectability it had enjoyed in the Seventies, Blair had gone much further. Certainly, Blair was an exceptionally attractive leader. But the party he brought to the election was also transformed: unashamedly embracing Margaret Thatcher's restructuring of the economy. It offered an ideological third way which would seek to heal the social divisions which that restructuring had brought in its wake. Neither old left, went the mantra, nor new right. No longer prepared to tax in order to spend, it also, for the first time in the party's history, promised less than it intended to deliver. And the electorate responded to Blair as it had to Thatcher in 1979, only more so.

The one party that can have truly been said to have benefited from the election campaign itself was the Liberal Democrat Party, which saw its vote share rise to 17 from 13 per cent. One of the peculiar features of the 1997 electorate was its ruthless use of tactical voting. As a result, the Liberal Democrats beat the system they had so long wanted to reform. The third party, with 46 seats, more than in any election since 1929, benefited to an extraordinary degree from the willingness of electors to vote indiscriminately for the anti-Tory candidate. And so did Labour: maybe Blair did "only" secure 44.6 per cent of the vote - more than in any election since 1970, though lower than any between 1945 and 1966. But the total anti-Tory vote of 61.6 per cent blasted all previous 20th- century records.

The scale of this defeat brought in its wake potential problems as well as untold advantages for Labour. Vigorous opposition and narrow majorities can be tough disciplinarians. The fact that Blair is confronting neither may have played a modest part in the revolt this month over the badly- managed cuts in lone-parent benefit. But those cuts are a harbinger for perhaps his toughest task. Welfare reform, while explicitly foreshadowed in the manifesto, was least discussed in detail before or during the election. Which is one reason why, as shown by the David Blunkett letter leaked last weekend, Cabinet ministers are agonising about some of it now. The ending of free university tuition - a hard choice managed with outstanding skill by that same David Blunkett - and the switch from legal aid to no- win no-fee lawyers' services, are both aspects of of welfare reform. But it also means a more far-reaching attempt than the Tories would have dared, to end the dependency culture and replace it with one of work; to lift the aspirations of those trapped in cut-off, no-hope estates, to target benefits to those who need them and reduce them for those who don't; and in the process find more money for education and health. Blair shows no sign of being diverted from this task; those who try to thwart him from the backbenches may have to face the consequences.

And he has the room to drive through the most ambitious programme of constitutional reform this century; to take just one example, the reform of the Lords which ran into the ground in the Sixties, is now, if not easy, attainable. On education and health, on youth justice, on the minimum wage, he has already begun to redeem his promises. But winning as new Labour means governing as new Labour. The one heresy he will never accept is the one that says since he won so massively it wasn't therefore necessary to transform the party as far as he did.