The launch of the R-Class this week is the sixth of those models. A six-seater crossover which Mercedes call a Grand Sports Tourer, it is an SUV with the emphasis on space and good driving dynamics.

The R-Class is the "bulkiest" model to date, coming with a standard wheelbase of 2980mm, or, in stretched version, 3515mm. There is also the choice of two petrol engines or a diesel engine.

This model's appeal is in its dimensions. It is a highmounted vehicle with the luxury one would expect from Mercedes but also lots of legroom for the second and third row of seats.

Fold these two away and there is enough space to carry items more than seven feet long. Headroom and width add to the feeling of spaciousness, and the driving position is excellent.

Owners will feel like kings of the road behind the wheel as the engines give plenty of power. The diesel is expected to be a strong seller with 244bhp and a top speed of 222km/h. It is priced at �?�79,530.

All vehicles have permanent four-wheel drive, eight airbags and lots of safety protection. The R350 petrol puts out 272bhp and has a maximum speed of 230km/h. The R500 meanwhile gives 306bhp and a top speed of 245km/h.

The two petrol models are priced at �?�79,530 and �?�99,070 respectively. Extra equipment in the Sports Pack costs �?�6,460 and a Styling Pack costs �?�5,637.

Fuel costs may not be an issue for motorists who can pay out these figures but everybody likes to think they are getting good value for money so the diesel's return of 9.3 litres per 100km must be considered good for such a big load-carrier.

Also impressive is the 7GTronic seven-speed automatic transmission which gives a seamless flow of power. Additionally, the vehicle is made safer by the electronically controlled traction system which helps keep the driver in check in even the worst driving conditions.

These are standard items, as is the air suspension for the rear wheels. Customers also have the option of Airmatic all-round air suspension with an adaptive damping system which automatically lowers by 20mm at high speeds to reduce wind resistance.

Mercedes has acknowledged that some highly technical software had in the past caused problems but this has now been rectified.

And customers who have suffered "unacceptable failure" of parts have been given replacements free of charge. This policy is to continue in vehicles where these faults occur.

Next July, a seven-seater GL-Class - an even bigger SUV - will appear as the final model from what Mercedes Benz call their second-product offensive.

The wave of new cars started in January 2005 with the A-Class now regarded as a "true Mercedes Benz" after some disappointment with earlier models.

Next came the highly stylish CLS in mid 2005.

They are still in great demand, as is the B-Class which launched in October when extra orders had to be urgently requested by importers MDL.

The M-Class is also in short supply as the factory has been unable to meet demand since the October launch. The new S-Class arrived in November and is now out-selling the competition as customers see it as a car more in keeping with the times than the previous model.