After a winter's afternoon spent tear-assing around in Poole Harbour, a thoroughly frozen Mrs F. sank into the SL55's heated seats, switched on the massage button and drifted off into the arms of Morpheous. I immediately began the Sleep Test. How fast could I drive without waking my passenger?

Is that the sound of eyebrows arching? Many enthusiasts will insist that the best way to test a 493bhp automobile is to grab it by the scruff of the neck and thrash it to an inch of its life. Please! Have a little respect. The SL55 may be Mercedes' fastest ever production automobile, but it is not a rally-bred Subaru. It's a Benz. It's a big, heavy, luxury car. Tradition dictates that the SL55's driver displays a certain amount of 'decorum'. Progress should be rapid, yet safe and effortless. Hence the Sleep Test.

Here's a good way to lose money. Take a mass-market saloon and spec it to the max: sat nav, heat insulated tinted glass, parking radar, Bi-Xenon headlights, 17" rubber, alloy wheels, sports suspension, Tiptronic gearbox and the biggest damn engine money can buy. Come trade-in time, you'll get just about the same money for your superfast gin palace as Mr. Repmobile gets for his plain vanilla version. And yet…

Your hi-spec mass-market machine will cost less than a bare bones prestige model. Case in point: the Volkswagen Passat W8 4Motion Sport. For £34,070, you get all the goodies above (including an eight-cylinder engine) for two hundred quid more than a no-spec six-cylinder BMW 530i Sport. The VW gives you more German automobile for less of your beloved English pounds, ja?