Motoring: The old ones are the best

To commemorate the 40th anniversary of the SL roadster, Mercedes has launched embellished special editions of its 320SL and 500SL. Don't send a birthday card. Since the 190SL was unveiled in 1955, and the 300SL roadster in 1957, such as celebration seems a little contrived.

But provided that buyers don't equate "special edition" with "solid investment" - SL resale values won't be much affected by the extra equipment - it matters little that the excuse for a party was motivated more by commerce than by sentiment.

The Millennium Dome will have seen paying customers before the launch of the next SL - spy photos show the prototype to be leaner, lower and more rounded than the model it will supplant - so Mercedes needs to market the present nine-year-old wundercar quite aggressively.

Jaguar's XK8, soon to be available with a supercharged engine, is one reason why Mercedes-Benz may find SLs increasingly difficult to shift. Price is another. The Special Editions don't come cheap, at pounds 66,630 for the SL 320 and pounds 83,630 for the SL500. M-B plan to make between 150 and 175 of each for the British market, the company's third-biggest, behind Germany and the US. Take it as read that they will all be beautifully assembled (on polished wood floors at a plant in Bremen), amazingly durable, ultra-safe and, provided they have V engines, blisteringly quick.

The 500SL on test was not a Special Edition, but extras (including alloy wheels that cost pounds 4,886) elevated its price to an SE-beating pounds 89,381. Such extravagance is in part justified by electronic aids that control wheelspin, skidding, cabin climate, speed, roll-over protection, mirror- dipping, even how the five-speed auto shifts its gears.

There's also the party-trick headgear, unlatching, furling and disappearing at the press of a button. You want for nothing, other than a soft, cosseting ride. For the average budget the 500SL is crazy money, of course. But you would need more - perhaps pounds 100,000 more - for an original 300SL roadster circa 1957/58. Half as much again might buy the race-bred 300SL Gullwing that sired it.

Even if classic prices are declining - and there's evidence to suggest they are - an original 300SL, open or closed, is as blue-chip as collectables come. No matter how special the edition, a 500SL will never acquire the status of a Gullwing, Merc's most coveted post-war car. Nor will the current flagship 600SL, powered by a 6.0-litre V12 engine of uncanny smoothness. Provenance, pedigree and scarcity determine these things.

The SL (super light) label is as much a misnomer as the "sports car" tag that goes with it. SLs are in fact heavyweight grand tourers, as good to be seen in as they are exemplary to drive. Even a tame, four-cylinder 190SL (1955-63) could cost pounds 25,000, according to Classic Car's price guide (a fully restored, ex-Ringo Starr 190SL was up for sale recently at pounds 35,000). The six-cylinder 230SL and 250SL that followed (1963-68) are today less valuable than the faster 280SL that ran from 1968 to 1971.

The real SL bargains can be found from the next series, made in the Seventies and Eighties. Merc's impeccable build quality has left many a worthy survivor languishing on the forecourts at Ford Escort money. There's no such thing as a trouble-free classic, but uppercrust Mercs come as close as you'll get.

Mercedes Benz 500SL

Specifications

Price: pounds 81,340. Engine: 4973cc, eight cylinders, 32 valves, 320bhp at 5600rpm. Five-speed automatic, rear wheel drive. Top speed 155mph (governed), 0-60 in 6.3 seconds

Rivals

Aston Martin DB7 Volante: pounds 92,500 (cheaper coupe, pounds 84,950). Great looks, lots of character, strong performance, Jaguar-based supercharged engine.

BMW M Roadster: pounds 40,570. Go-faster version of the two-seater convertible. Great to drive, very fast. Same 320bhp engine in M3 convertible.

Jaguar XK8 convertible: pounds 56,625 (coupe pounds 49,625). Head-turning presence, lovely V8 engine, very smooth, rides and handles well. Coming: supercharged XKR, blisteringly quick.