As well as being thief-friendly, convertibles weigh more than their hard-topped equivalents, use more petrol, cost more to insure, and are structually weaker so they handle like warm lettuce. But last year 43,653 people eschewed the modesty of tin roofs; and the market for wind-in-hair, flies-in-teeth motoring sits solidly at around 3% of new UK car sales.

So why do people want them? Precisely for all these reasons, says automotive trend analyst Steven Jacobs. "It's a sybaritic thing - a cabrio sends out a message that you can afford the implied costs. Even if the hood is up, it signals that you're a fun-loving driver."

Jacobs' argument might explains why the only diesel drop-top you can buy in the UK is from Quantum, a maker of Ford-based kit-cars. Diesel Car magazine says its readers often ask why they can't buy a non-petrol cabrio. Spokesman Mike Orford explains: "Derv and open-topped driving are accepted on the continent - both Audi and VW sell the combination, but you'll never see it here because UK drivers have a bizarre attitude. They automatically accept that cabrio driving is nothing to do with sensible, low-cost motoring."

If you're undeterred and feel you must join the al fresco set, the good news is that the choices are getting more exotic and less mainstream. Along with Vauxhall, Mitsubishi, Nissan and Citroën, Ford no longer offers a hooded option and, while a few of its rivals muster soft-top derivatives of their own chief sellers, the options are as sexy as sequinned wellies. So if you're serious about your purchase, it's better to go for a purpose-built cabrio.