Aha! I knew it was you who called

Ann Treneman on the nation's latest obsession

Do you have a secret? If so, don't pick up the phone - 1471 is stalking the land. That is the number for "call return", introduced only last December, and now being dialled a staggering 8 million times a day by Britons who want to find out who called them last.

This facility can be helpful if you suspect someone is having an affair, skiving off work or just plain lying about their whereabouts. There have been cases of divorce after wayward men rang home and claimed to be delayed at work. A quick 1471 showed that they were, in fact, in a pub down the road.

"It's the first thing I do when I get home from work," says one young woman. She is 22 and speaks for her generation: an Oftel survey shows that 80 per cent of people aged 16 to 24 use call return, compared with 50 per cent of those aged 65 and over.

"There is something driven about 1471," says Guy Fielding of Queen Margaret College, Edinburgh. He attributes this to the Zeigarnik Effect - after the German psychologist Elizabeth Zeigarnik - which says that our memories only let go of tasks when they are complete. In the case of 1471, the "conversation task" begins when you realise someone has called you; only by ringing back can you complete it.

The embarrassing bit is that we are all floundering in an etiquette vacuum. What is the form when you just can't stop yourself from returning a call but have no idea who you are ringing? "Who are you?" seems a bit much when you have placed the call. And what if you ring someone but suddenly decide you cannot cope and hang up? They ring you back and there is a moment of phone hell.

Saddest, of all is the demise of the romantic notion of telepathy. "Isn't that strange? I've just tried to call you," says the person you are ringing. It's not destiny, though, just digital dialling,

The most explosive territory of all is the 1471 message, "the caller has withheld their number". Who does this? Obscene callers, for starters - and call return has cut the number of these and hoax calls by 20 per cent. Then there are the spies, the cheats, the plain paranoid.

You can block individual calls by dialling 141 beforehand, or you can have all calls blocked permanently. Less than half a million lines out of 27 million have opted for this. Some large companies do so for technical reasons, but the rest are the rich, the famous, the weird and the frightened. Even they can choose to override the block by dialling 1471 before a call. For once with a British utility it really is nice to be in control.

Not so for the scriptwriters. The plot of Thelma and Louise would crumble without the frantic attempts to trace calls as they head west. In Mission Impossible, the most sophisticated spies in the world try to track a call from Tom Cruise. But why all this fuss when they could just dial 1471?