The key phrase of today is: “Have your say.” All broadcasters and journalists are involved in a campaign against reticence: text your opinion, vote on this, join the debate. It’s as though they want to turn us all into big-heads so that they can feel better about being such big-heads themselves. The climate is such that you begin to appear stand-offish if, like me, you’ve never written a blog, reviewed an Amazon title, called a phone-in; if you’re not on Facebook, if your ringtone is not particularly exotic, if you don’t wear a ribbon for some cause . . . and if your car registration plate is not personalised.

There’s been a market in interesting registrations ever since cars were invented. It grew to the extent that, in 1989, the Driver and Vehicle Licensing Agency itself muscled in, reserving any registrations that seemed characterful and selling them at prices ranging from £250 to £250,000 (the price paid for 5INGH in April this year). In 1990/91, the DVLA sold 25,000 personalised plates. The figure for 2006/2007 is 243,000 and, as I cycle around London, it seems that every other car is flashing some more or less cryptic message.

Here are the plates I saw in five minutes of bicycling recently: 1000 RO, OIL 9150, ANG 2,VIP OB and J15 YCE, which was on a beautiful sky-blue Bentley, and made me wonder about the royalties that might have accrued to the descendants of James Joyce.

A disproportionate number of personalised plates are attached to cars with smoked-glass windows. Well, do the drivers want to be noticed or not? You’d have thought so, since many plates only “work” if you see the owner. I noticed a sporty, purple car in Highgate with the registration B1 LAK. If a white guy drove around in that, everyone would just be baffled.

Context is everything. I used to see a black Daimler (or similar) in central London bearing the registration 1 KEN, and for months I was made indignant by the thought that this might be the runabout of that purported egalitarian, Ken Livingstone. But then I saw it parked outside the Kenyan high commission in Portland Place. A plate reading SNO3 ETC made sense when I saw it in the teachers’ car park of a private school.

Other plates practically force you to stare at the owner in order to crack the code. I stopped at a traffic light next to SJ 1942, but the woman driving (Sarah Jane, perhaps?) didn’t seem older than the mid-thirties. At the time of writing, I have just come in from seeing the plate B16 MBR. My eye was tricked into reading the 6 as a “G”, but it was hard to say about the pale, bespectacled chap at the wheel. He certainly had a big car.

Sometimes the plates seem provocative, meant to remind you that you are not super-rich. I am often overtaken by a local car bearing LEF 1W, and am tormented that it appears to be saying: “Left You”. But some are beautiful. I liked A11 URE, which I saw on a battered van in Mayfair, and M1 STY Y, on a Mini in Highgate (the superfluous “Y” made it even more endearing).

A friend of mine recently irritated me by buying a very nice Jaguar, which he pronounces “Jagwar”. The interior is immaculate, middle-class perfection. On the back shelf are a guide to the cathedral cities of England and a golfing umbrella, and naturally it has a personalised plate.

It isn’t one of the expensive, universally comprehensible ones. To appreciate it, you have to know my friend’s middle name, but I had a bit of a go at him anyway. Wasn’t the plate just sheer boasting? He didn’t bother arguing back, but just grinned at me as though my agonising were quaint and ridiculous. I felt similarly disoriented the other day when a car slowed and with great good manners allowed me to cross the road with my son. The registration? Y 1OSE. l