Money and ratings shout louder than ITN headlines: Virtually every memorable piece of breaking news in the last three years made it to the early evening bulletins

ALL broadcasters with the power to change schedules have to live with what you might call the Archers factor. They soon learn (painfully, in most cases) how closely private lives can become interwoven with the transmission of popular programmes, often growing together so intimately that change to one is impossible without painful wrenching of the other.

No anaesthetic for this operation has yet been discovered and news readers, politicians and television executives are no more immune to its pains than the ordinary listener who has built her day around Woman's Hour. They can, though, scream far more loudly, and are more adept at couching private sentiment in terms of the public good. It is at least one of the reasons why proposals to change the timing of News at Ten have caused such a flurry of well-publicised indignation.

Many would argue, of course, that this is far more than a matter of disrupted routine. They would contend that the 10pm slot confers a particular merit on the bulletin, which is now synchronised with Parliament and the American working day. It was telling, though, that Sir Alastair Burnet - a former News at Ten presenter and chief defender of the status quo - had to go back as far as the fall of the Callaghan government to find an example of a major news event that happened while News at Ten was on the air.

Virtually every memorable piece of breaking news in the last three years - Margaret Thatcher's decision to fight a second round of the leadership battle, Norman Lamont's sacking, Sir Geoffrey Howe's resignation speech, the Soviet coup, John McCarthy's release - made it to the early evening bulletins. Sometimes only just - Nigel Lawson resigned at 5.58pm, resulting in a flustered 6pm BBC bulletin - but certainly not late enough to suggest that a 10pm slot is indispensable or that a 6.30pm broadcast would be hamstrung. It is not so much when you do it that matters, but what you do.

It is true that there is no guarantee that ITV's flagship news bulletin will be as carefully guarded once the patina of inviolability has been removed. But there are grounds for a more sanguine view, none of which require a nave trust in the benevolent motives of ITV's bosses. News at Ten is an important revenue-earner, delivering the AB viewers that advertisers value (its break is the highest-priced slot in the evening). In addition, like all news bulletins, it provides a guilt-free entry to an evening's viewing ('I'm just going to look at the headlines' being one of the most frequently used excuses for turning the set on). Even the most venal programme controller should recognise the simple commercial merits of a distinguished entrance hall to the store. As such it may simply be too valuable to leave in the late evening, where it also constricts the possibilities for high-earning films.

But this tremor in the world of British television is only the aftershock. The earthquake, which took place a few years ago, was the 1990 Broadcasting Act. Before that legislation, News at Ten was effectively an immovable object; after it, the only requirement on franchise holders was to broadcast a news programme some time between 6.30pm and 10.30pm (a detail that was not widely discussed at the time but should have sent a shudder through the ITN building).

The Independent Television Commission could have ring-fenced News at Ten when it was briefing franchise applicants, but it did not, and it is now left to wring its hands ineffectually as the companies it created seek to meet the very large bills that are coming due. Other tremors have shaken the calculations that were made with such confidence a few years ago: the two satellite channels have merged, combining their forces against terrestrial broadcasters; Channel 4 has grown up and left home and is proving uncomfortably successful at selling its own advertising; the recession, that all-purpose scapegoat, has knocked even cautious projections (and some were not cautious) out of true. The changes proposed for ITV's principal bulletin are the consequence of a fundamental shift in the principles of commercial broadcasting, not evidence that it has just begun.

'I do not think I am exaggerating when I say that moving News at Ten means the end of serious commercial television,' Sir David Nicholas warned in one of the more impassioned contributions to the weekend's debate. He might as accurately have noted that the end of serious commercial television made it inevitable that News at Ten would move.

This does not necessarily mean that the protesters are wrong in their gloomy predictions. Certainly the proposal is another wedge in the widening gap between the fundamental instincts of the BBC and ITV. When Sir Alastair noted that 'plain people can go to bed afterwards knowing what the day has brought', you could catch a whiff of the patrician condescension that has protected News at Ten for so long. Having delivered the circus of prime-time soaps and game shows, ITV said its prayers before bedtime.

There is not, in fact, much evidence that the plain people are very worried about this change in the schedules. But Sir Alastair represents a time when the fancy people (who stay up to watch Newsnight) felt an obligation to give them what they needed rather than what they wanted. That attitude has a distinguished record of achievement in the history of British television. However much we may lament it, it is fundamentally anachronistic in the world of deregulated television.