WHAT is it about boys and lights? Why do they always switch them on and never, ever switch them off again?

I could probably save myself a fortune with the amount of needless electricity they burn. Enough for some new boots, a holiday, a flat in town...

It's not as though they're afraid of the dark. Even when they were little, they rarely panicked about monsters under the bed or on top of the wardrobe, and didn't demand a nightlight.

True, we left the landing light on for many years, to stop them falling down the stairs when they got up in the night. Then there were a few years of darkness until we started leaving the hall light on to stop them falling over the doorstep when they came in from a night on the razz.

That's a bit pointless too - it's generally broad daylight before they come rolling home.

There was a time - gosh, hard to believe - when they sweetly wanted to save the planet. They had pictures of endangered species on their bedroom walls, lectured me about fossil fuels and made me buy expensive energy-saving light bulbs.

That didn't last long.

Now as they walk through any doorway, you can see their hand in a reflex action feeling for the light switch to put it on. Funnily enough, this same reflex action doesn't work in reverse. The lights may be going out all over England, but never in our house.

We have lots of table lamps. The boys like those. But just to be sure, they put the overhead lamps on too. In midsummer, we could pass for one of those houses all lit up for Christmas.

And then the boys go out. But not the lights. "It's to put the burglars off," they say.

Well actually, any self-respecting burglar looking into the sitting room in the state the boys usually leave it would think they'd been beaten to it by another gang and probably not bother. So they might just have a point.

The only time, the one and only time, the boys ever put a light out is when I'm in the study. They will come in to ask me something, then leave, switching off the light on their way and leaving me in the dark with only the glow of the computer screen to see by.

"It's only a light bulb," they say, when I moan about the electricity bill. But it's not only one.

On Monday evening I was out in the garden looking into the house and I counted 13 lights on. Thirteen! It was like a little radar screen of their progress round the house.

Meanwhile, I was in the garden cutting the grass. You know what that means, don't you? They had 13 lights on and it wasn't even dark!

They leave home on Sunday. Northern Electric's profits will plummet.

It won't be long, of course, before the boys will have to pay their own electricity bills. Maybe that'll be the day they finally find the off switch.