Back in 1996, when Mercedes-Benz launched the original SLK, it was the first two-seater sports car with a folding metal hard top. The idea was an instant success and gave birth to a new generation of coupé-cabriolets (CCs).

So when in 2004 Mercedes-Benz revealed an all-new SLK, expectations were high. What new innovation would this car bring? A tad disappointingly, the answer was: none. But then again, it didn’t really need any more gimmicks.

What it did deliver was an improvement in exterior styling and interior space. The new-model SLK took styling cues not only from its big brother the SL but also from the SLR supercar. Being both longer and wider, it provided a noticeably roomier cabin, and thanks to a revised folding roof mechanism Mercedes managed to liberate a useful amount of extra boot space.

Under the SLK’s attractive bonnet comes a lineup of four petrol engines offering power outputs to suit all tastes. Badged rather misleadingly, the SLK 200 Kompressor – the entry-level model – is powered by a supercharged 1.8 litre motor producing 163bhp. While the power may sound modest, the supercharger produces generous torque, and the 0-60mph time of about 8sec is pretty good.

Next comes the SLK 280, which – confusingly, again – has a naturally aspirated 3 litre engine producing 231bhp and capable of powering the SLK from 0 to 60mph in a very respectable 6.3sec.

But the pick of the bunch is the SLK 350, costing about £2,000 more than a used 280 and providing 272bhp and a spirited 0-60mph time of 5.5sec. Performance of this ilk is more than enough for most buyers, yet if more is needed, the SLK is happy to oblige, courtesy of the 5.5 litre AMG version. Its 360bhp lets you hit 60mph from rest in less than 5sec. As many owners are starting to discover, a used SLK 55 at, say, £25,000 makes a new SL 55 costing £100,000 look somewhat overpriced.

You have the choice of manual or automatic transmission on all but the AMG model (which uses a seven-speed, paddle-shift auto). Usually it’s easy to make a decision about a gearbox on a Mercedes: you buy the automatic. But the new SLK muddies the water by having the best manual box for years. Only die-hard auto-box operators should discount the terrific six-speed manual – it is, after all, about £2,000 cheaper and in most circumstances more satisfying to use.

Slip behind the wheel of the SLK and it all feels just right, the centre console and dials conveying a satisfyingly upmarket feel. The sports seats, almost inevitably trimmed in leather, are of a decent size, and even with the roof in place there is good headroom.

Press a button and in 22sec your coupé converts into a drop top ready for you to enjoy fresh-air motoring. On the road it’s immediately obvious that the SLK has a very rigid structure with virtually no scuttle shake. There is also a marked improvement in the steering and suspension, and while the chassis may not be as ultimately engaging as that of a Porsche Boxster, the SLK is certainly hot on the heels of a BMW Z4, delivering a compliant, relaxing ride married with sure-footed, precise handling.

As with most Mercedes-Benz models, a new SLK came with a long list of factory options, so used examples are rarely identically equipped or priced. The big favourites with buyers of used models are the larger alloy wheels, sports exhausts and satellite navigation, while leather seats, automatic wipers and xenon headlights are pretty much expected. Be careful not to pay a premium for someone else’s taste though.

When buying a used SLK it’s vital to have a complete service history. The variable service schedule means there’s no set servicing interval, but expect to see at least an annual dealer stamp, and ask to see original receipts for repairs.

The latest Mercedes-Benz SLK did more than hold steady the success of the original; it managed to elevate it to being one of the most usable and desirable sports cars in the world.

Gearbox The six-speed manual is the best Mercedes manual box in years. The auto box gives slightly better acceleration and economy figures

Roof operation Just one button raises or lowers the roof in a modest 22sec. A factory option also lets you do this using the remote key fob

Airscarf A “scarf” of warm air through the headrest vents keeps front-seat occupants cosy on cold days when the roof is down

Alloys Check for kerbing as refurbishment can be expensive, especially on the larger 18in AMG alloys

Steering The latest SLK has rack-and-pinion steering, a vast improvement on the previous model. Many buyers also chose the factory-option speed-sensitive steering

Suspension Optional sports suspension lowers ride height by 10mm and improves handling while still providing a reasonable ride quality

Boot 208 litres of cargo volume with the roof stored in the boot, and that’s an improvement on the original model, though still enough for only modest amounts of luggage

Stereo Standard unit is impressive enough; the optional CD stacker swallows up glovebox space

Tail-lights LED-type rear lights illuminate quicker than conventional bulbs, providing earlier warning of braking to vehicles behind you

Vital statistics

Model Mercedes-Benz SLK 350 (Tip)

Engine 3498cc, eight cylinders

Power 272bhp

Transmission Seven-speed automatic

Fuel 28mpg (combined)

Acceleration 0-60mph: 5.5sec

Top speed 155mph (limited)

CO2 emissions 242g/km

Road tax band G (£300 a year)

Cost new today £37,402

The one to buy

SLK 350 auto, 2005 05 with 20,000 miles. Pay £26,250 at a dealer, or £25,000 privately

Values

Mileage 10,000 20,000 40,000

2004 04 Trade £22,100 £21,050 £18,950

Retail £25,250 £24,250 £22,000

2005 05 Trade £24,250 £23,050 £20,700

Retail £27,250 £26,250 £24,000

2006 06 Trade £26,300 £25,000 £22,550

Retail £29,500 £28,000 £25,500

Or for similar money

2003 53 Lexus SC430

2005 05 Porsche Boxster 3.2 S

2006 56 Audi TT 3.2 V6 quattro

2007 07 BMW Z4 3.0Si Sport

2007 07 Nissan 350Z Roadster