IN THIS FEATURE Open to debate Petrol preferred

When I drove Vauxhall's Tigra roadster at its original launch last year, I enjoyed it immensely: the little two-seater is flawed, but its easy-going character, the free-revving, lively 90bhp 1.4-litre petrol engine and good-quality, pleasant cabin were all endearing factors. Sure, forward visibility isn't great, with thick, slanted windscreen pillars, rearward vision is even more restricted, thanks to the rollover bars (the silver wave-shaped structure behind the seats) and wind deflector, and ride quality is not perfect. There's also the infuriating push-button remote boot opening/closing, which takes ages and is immensely frustrating when all you want to do is shove a bag away, slam and go. But these are small details which besotted buyers would be more than prepared to put up with.

Now the Tigra comes with a new option: the GM-Fiat 1.3-litre diesel engine, giving 70bhp. Diesel convertibles aren't unique - versions of the Audi A4, BMW 3-Series and Saab 9-3 drop-tops with diesel engines are either already on sale or on the way - but in the supermini-sized sector, only the Peugeot 206 CC comes with such an option. The Tigra CDTi promises to be much more economical than the 1.6-litre 206 CC HDI, though: the little Multijet engine, as used in the Fiats Panda and Punto as well as the Corsa, is claimed to return an excellent 61.4mpg (combined). Added to this, it falls into very low categories for road tax and company car tax, because it emits just 124g/km of carbon dioxide.

Tin top is more secure, but mechanism adds weight

So not only is the Tigra cute-looking, it's also relatively practical and easy to live with, thanks to its metal electrically-folding roof, which protects it from thieves and offers better insulation than a traditional canvas hood. And with this diesel engine, it promises to be very cheap to run as well. Time to treat yourself to a really sensible sports car?