In a very clear admission that there are boy racers in the boardroom, Mercedes recently veered a little way off its traditionally elegant path to come up with a Sport edition of the suave C-Class saloon.

The four-door flyer, not to be confused with the three-door C-Class Sports Coupe, has go-faster add-ons that are about as subtle as Chancellor Gordon Brown's bid for No 10, yet it doesn't cost anything like Mercedes' iconic quickie, the AMG.

There's half-a-dozen Sport editions in the C-Class range, in petrol and diesel form, and the £34,150 C320 CDi, trialled here, is, for example, some £15,000 less than the AMG it clearly copies - yet only a little bit slower.

The diesel six-cylinder C320 CDi Sport has a 155mph limited top speed, and doesn't look too sluggish up to the 62mph mark, with a 7.2-second acceleration figure against the awesome AMG's 5.4 seconds.

There the comparison ends, though: the AMG is a specialist badge-within-a-badge buy, and very much a one-off. The diesel Sport, on the other hand, is a superlative executive machine at a more accessible price that will keep any company accountant more than happy.

This particular oil-burner of 37.2mpg combined-cycle ability, will have a considerably lower fuel bill over three years/60,000 miles than a petrol equivalent, and also look good on paper when assessing the benefit in kind for a 40% tax payer. That 2987cc engine, with 224bhp to deliver to the family-sized Merc's back wheels through an automatic gearbox, is more than just a premium-market money-saver. It puts up the strongest possible case for being the smoothest, quietest, and most quick-witted oil-burner on the market today.

What's more, the C320 CDi Sport is an inspiring performer. Lowered and tuned suspension, perfectly weighted power steering, electronic stability with anti-skid control, figure-hugging seats, wider tyres, negligible body roll and limpet grip all harmonise to pump up your confidence no end.

For the overall package, Mercedes is right on the money: a Porsche Boxster is similarly priced, only a shade faster to 62mph, and a heck of a lot less practical.