EVEN if you aren't blessed with an encyclopaedic knowledge of how the emissions-based company car tax scheme will work, fleet managers by now should have cottoned on to one fact: the fewer CO2 particles emitted, the cheaper the tax bill will be at the end of the year. And few cars meet this demand better than the Audi A2.

So what's Audi's secret? Using technology first pioneered in the A8 saloon, the A2 is the world's first volume production car to use a chassis constructed entirely from aluminium. Remarkably, Audi's Space Frame technology not only maintains similar torsional rigidity strengths of conventional steel but the A2 weighs an incredible 43% less, giving the A2 the lightest kerb weight in the class at just 895kg.

The A2 comes in one bodystyle and engine choice: the 1.4-litre 16-valve four-cylinder petrol developing 75bhp (tested here) carried over from the Volkswagen Lupo and Polo ranges. Early next year, a three-cylinder 1.4-litre turbodiesel also with 75bhp (and also from the Lupo and Polo) arrives. With such a light load to lug, performance is much better than you might expect considering the engine's diminutive capacity, but it also means they are both mega-economical.

Even in petrol form the A2 manages to return 47.1mpg - the diesel reaches 66mpg. With such frugality, logic dictates the Audi A2 must also be amazingly clean and in petrol format it records 144g/km.

But these pictures do not do justice to the A2's tiny proportions. At 1.67metres wide, it's 13cm narrower than a Ford Fiesta and standing 1.55metres tall it is 17cm shorter than a Renault Scenic. To counteract any packaging deficiencies, Audi has engineered a Space Floor Concept with a split-level floor in which the rear-seat passengers sit below the front pair, thus liberating head and kneeroom.

Entry-level pricing for the A2 starts at ú13,150 on-the-road for the A2 1.4, rising to ú16,600 for the A2 1.4 TDI SE. The 1.4 16v SE costs ú14,920.