Most open cars which spend at least some of their time on business are four-seat convertible versions of saloons, but it is surprising how many people manage to justify running a two-seater on a company account. Of course, if you have no real need to haul three passengers around, why not go for the fun of the thing?

Some two-seaters, or two-plus-twos for manufacturers who are feeling optimistic, are open-top adaptations of a coupe design. There are some purposeful high-performance cars in this group, the Ferrari F355, Aston Martin DB7, Porsche Carrera 911, Jaguar XK8 and XKR notable among them. In a sub-division you can include the Alfa Romeo Spider, a spectacular car with slam-it-to-them styling, and the Toyota Celica.

Then there are the examples with no fixed-roof variant. We are in sports car territory here, but the best of these are perfectly reasonable all-week transport. The MGF and Mazda MX-5 are among the middle-sized types, while the Lotus Elise is a no-compromise brilliant handler. Smaller British-owned manufacturers, in a part of the market where ''comfortable'' and ''well equipped'' may be rather variable definitions, chip in with cars like Morgan, Marcos and TVR.

It is sometimes forgotten that the Germans are well represented in the two-seater open-car market. BMW began with the retro-styled and modestly powered 1.9-litre Z3 roadster, but has extended that range to include a more powerful 2.8 and the formidable M Roadster.

The Mercedes SLK with its neat roof-into-the-boot arrangement can be a coupe at one moment, and a convertible about 15 seconds later. The top class two-seater in the Mercedes catalogue is the SL, which comes with a choice of 2.8, 3.2, five-litre and six-litre engines. When you get to the AMG-modified SL60, you are talking about one of the world's great road cars.