There are, as Princess Diana memorably observed, three people in this marriage.

The late Princess of Wales was referring to her husband's relationship with the then Camilla Parker-Bowles.

My rival doesn't have a name. She doesn't even have a little finger – but if she did you can bet that my husband would be twisted around it.

If she tells him to do something, then he dutifully complies. Like so many men nowadays, he has become smitten with his sat-nav.

On just about every journey, we are now accompanied by the disembodied female voice of the sav-nat, which has an irksome habit of interrupting a song I'm enjoying on the radio to announce: "In 200 yards, take a left turn".

At least now I understand why there are so many stories in the papers nowadays about blokes getting their cars stuck down farm tracks.

The sat-nav told them to do it, and they obeyed.

Only a few months ago, a lorry got wedged in a nearby alleyway that is so narrow, I wouldn't trust myself to push a supermarket trolley down it. But the lorry driver's sat-nav told him to drive down that route, so off he went.

What is wrong with a bit of good-old fashioned map reading? Or asking for directions? Or even common sense?

Of course, I'd forgotten that most men would prefer doing several circuits of Southville's one-way streets to suffering the public humiliation of rolling down their window and asking how to get to somewhere. As for maps, it seems that no self-respecting male will demean himself to bothering with such steam age technology when there is a gadget that can be twiddled with instead.

So most of our journeys now begin with place names and streets being programmed into the beloved sat-nav, while I seethe in the passenger seat. My husband even once told me: "You have many fine qualities, but map reading is not one of them." Actually, I think I'm a brilliant map reader, but I usually have more important things to do when in the car. This is possibly why no sat-nav is based upon my style of navigating.

In fact, sat-navs based upon personal idiosyncrasies when navigating could be very interesting. Just take the following examples…

"Sav"-nav: A product based upon the navigational skills of someone connected to this column. Claims to be map-reading, but is more likely to be flicking busily between radio channels to avoid the adverts, or trying to skip dud tracks on the CD.

Sample dialogue: "What do you mean I've got to expect adverts on the radio stations I listen to? You don't expect me to listen to Radio Bristol, do you? Doh!"

Verdict: Erratic and prone to overshooting vital turnings as a result of being engrossed in jumping between radio stations. But you will never have to listen to an advert or dud song again.

"Bris"-nav: A navigational instrument designed for the unique challenges of driving in Bristol.

Sample dialogue: "When you have made your way to the end of the line of almost stationary traffic, turn left and join the traffic jam. When the traffic jam has cleared, join the roundabout. Then turn off your ignition and wait because a bus is blocking your exit."

Verdict: A generally useless device with minor value as a means of distraction as you crawl along the streets of Bristol bumper-to bumper.

"Chav"-nav: Designed for those who consider the road to be their racetrack, and have little regard for their vehicle – often because it does not belong to them anyway.

Sample dialogue: "Rev the accelerator as hard as you can a few times. Then go down the road tailgating that old biddy in the Morris Minor. Watch out, there's a police car! Do a U-turn at the bottom of the road, then put your foot down to get rid of them."

Verdict: Not suitable for nervous drivers, or anyone who wishes to retain their driving licence.

"Pav"-nav: A navigation system for those who have become so used to being told exactly what to do when driving that they are no longer capable of walking along a pavement without receiving full instructions.

Sample dialogue: "Keep walking until you get to the pedestrian crossing. Wait for the green man, then cross the road. Keep walking up the road, past the post box, and past the second lamppost. When you get to the red front door on the right, put your key in the lock and turn. Don't forget to shut the front door behind you when you get inside."

Verdict: Could become the new gadget of choice for the sat-nav and predictive text generation.