Historians still puzzle over these questions. The fact is that, half a century on, we have difficulty understanding millennial Britain. The government celebrated the epochal moment by investing hundreds of millions in a mighty construct designed to last no more than a decade. Politics had become wilfully futile. The new form of popular entertainment - watching celebrities rise from obscurity and then destroy themselves in a variety of amusing ways - served to remind the people not of the triumph of the human spirit but of its mediocrity and greed. The grand Millennium had arrived at last, and yet everything was unusually trivial and demeaning. What on earth was going on?
The most convincing historical theory is that 1999 was the crowning moment of what has become known as the Age of Irony. The lack of seriousness was not only intentional; it was the cultural keynote of the time. So a singer called George Michael, whose career had been threatened by a sexual incident in a lavatory, responded by producing a self-promotional video parodying his own personal embarrassment, to the soundtrack of his latest hit. As for other music, the newspapers gravely reported a titanic struggle between a naff 1970s hit revived by a "boy band" and a merciless take-off of pop Christianity by the satirist Sir Cliff Richard.
To all intents and purposes, political life had disappeared. The opposition provided little more than light entertainment, while the government, with a deft sense of irony, had replaced policy with empty gestures accompanied by reassuring words from its accomplished marketing department.
In place of politics, Britons were offered a series of public dramas, in which minor politicians and iffy tycoons enacted various aspects of human weakness. Lust and hubris were represented by the hack novelist Jeffrey Archer; suburban greed and ambition by a former MP called Hamilton, whose tussle over a matter of libel with Fayed, a bullying businessman from the Middle East, was described, in true Age of Irony manner, as "the court case of the century".
Behind those pantomime figures, associated dramas of grinding triviality dominated the headlines. "All intimacy has been lost," wailed one of Archer's mistresses in a newspaper expose published on the last Sunday of the century. On the same day, Hamilton's wife, Christine, compared losing the case to being hanged. "How many innocent people have been executed like this?" she asked. "Until now I believed in capital punishment, but this has changed my mind."
In the Age of Irony, the joke was everything. No sector was making more absurd amounts of money than football - so the government took pounds 20m from vulnerable saps gulled into playing an ironic gambling game called the Lottery to build a national football stadium. A foreign power would no longer be permitted to attack civilians with impunity, ministers had announced that year - so they stood idly by as Russia did just that. The problems of homelessness were as bad as ever, so soup kitchens were rationalised.
On TV, a programme called The Royle Family was the hit of the season. Featuring a working-class family bickering lazily in front of a blaring TV set, it provided a perfect emblem of millennial Britain - slack, sentimental, defeated and, above all, ironic - as the battered century came to its oddly ignominious close.