Saturday night is (just about) all right...

ITV should have known it's an institution. Tamper at your peril.

Some fret that every British institution is crumbling. Universities aren't what they were. Parliament is a shadow of its former self. Even baked beans on toast lack the old kick with low-sugar beans and wholemeal bread. But fear not: some things are sacred. ITV has just learned, to its great cost, that Saturday night is a festival you can't easily tinker with. Des Lynam's The Premiership was screened at 7pm. Audience figures collapsed. It's now being shifted back to Match of the Day's old BBC-style slot, after 10pm.

TV executives hired more women presenters, hoping to make soccer less blokey. But the Match of the Day ritual meant buying a manly six-pack on the way back from the pub, and no one wanted to come back too early. Surveys show that the pub is the nation's favourite leisure choice. In most streets of most towns, despite the female-friendly rise of the mega-bar, it remains a bastion of blokeyness, especially on Saturday nights.

How did Saturday night become the great weekly gala? Until the trade unions achieved a gradual shortening of hours, the British working week ran from Monday morning to Saturday teatime. Next day lay the classic wearisome Sunday, with no football, cinema or superstore shopping. So this night was a precious few hours of irresponsibility. It was the weekly equivalent of the annual outing to Blackpool, Margate or Skegness. For a few hours, you spent like Croesus. Nobody was your boss.

The classic fictional account is Alan Sillitoe's Saturday Night and Sunday Morning (later a notably grim 1960 film, where the hangover got more attention than the spree). Even John Travolta's Saturday Night Fever, it's worth remembering, was based on a magazine article by a British journalist that, he's since confessed, was simply invented. Short of time to interview the American teenagers he was supposedly reporting on, he just drew on his recollections of orgiastic Saturday nights back in Britain. The refrain of the old rugby club song captures the spirit (or the hope): "If you don't get shagged on a Saturday night, you'll never get shagged at all." The columnist, Simon Hoggart, recently asked himself what the clearest sign of ageing was. His answer: when you're glad not to have an invitation to go out on a Saturday night.

Nothing is ever quite static, of course. Saturday night fever has spread to other days. On Friday nights in London's West End, or Canal Street in Manchester, you are squeezed among a mass of drinkers. A London School of Economics study of cultural conflicts in the West End, out this month, found more complaints about noise from bars and restaurants on a Friday than on a Saturday.

The most striking change, down the years, is the rise of the club. I looked back at the London listings magazine, Time Out, for the final weeks of October 1971, 1981, 1991 and 2001. At first, there were only enough clubs to fill a column or so: mostly jazz or folk, like Hobbit's Garden in Wimbledon. By 1981, the list had doubled, and included Dingwall's at Camden Lock ("dress optional"), Heaven ("the largest and most sophisticated gay club in Europe") and Stringfellows ("London's answer to Studio 54"). A decade later, the wave of club fashion was unstoppable, with 10 columns of "rap, ragga, reggae, with some swingbeats and soulful boogie thrown in". And last week it was 13 columns.

Delving back into these long-lost strata of past Saturday nights immunises you against any notion that there was a golden age of either elite or popular culture. If you switched on the box on the last Saturday evening in October 1971, BBC1 led you from Bruce Forsyth's Generation Game, through The Harry Secombe Show (with Vera Lynn) and Frankie Howerd's comedy series, Up Pompeii (with Barbara Windsor as Nymphia), and on to Match of the Day at 10.20. A decade on, the offer had slightly changed. The impressionist, Mike Yarwood, had crept in, as had Michael Parkinson, but the evening still began with The Generation Game (with Larry Grayson) and ended with Match of the Day. By 1991, it was Bruce Forsyth again. And yesterday it was The Generation Game again.

Statisticians report that Saturday is the nation's favourite day for watching videos. The entertainment heyday, once, of sweet Saturday night, was the music hall. Marie Lloyd and her successors belted out "A little of what you fancy does you good", and "If you show the boys just a little bit, it's the little bit the boys admire". Vaudeville's essence was repetition; the same songs from the same stars, the same catchlines from the same comedians.

Television took over where music hall left off. Its Saturdays, especially, have always been more of the same. Saturday night is, perhaps reassuringly, a monument to British conservatism.

Paul Barker is a senior research fellow, Institute of Community Studies