The Mercedes-Benz R-Class is one of the most difficult cars on the road to shove into a neat pigeon-hole.

Part sports saloon, part estate and part people carrier, the six-seater R-Class also has permanent four-wheel-drive, to add a hint of macho sports utility vehicle to the already confusing mix.

Even Mercedes had a problem with what to call it, so they came up with the name Grand Sports Tourer.

It is certainly grand, especially in the long wheelbase version which gives masses of leather, walnut and chrome-trimmed interior.

Sports in that engines start at 220 horsepower and move up in power output, and tourer in that it will carry six people in total comfort.

The seven-speed automatic gearbox delivers brisk acceleration and impressive fuel consumption.

The small steps between ratios also mean that gear changes are virtually imperceptible, while electronic control means that at, say, 60mph, the engine speed will be about 12 per cent lower than with a five-speed automatic, contributing to the R-Class's sense of relaxed performance.

The R-Class is every bit as long as a luxury saloon, but much more spacious inside, since about two-thirds of the overall length is given over to its six occupants.

And it has the clear edge in versatility over a large luxury saloon in that the four rear seats can be individually and quickly folded, to create a flat floor, opening up a load area that rivals a small van. Lots of interior space demands powerful heating and ventilation to match and every R-Class boasts automatic climate control which is equally capable of cooling down the interior quickly on a hot summer's day as it is at keeping passengers snug and warm in the depths of winter.

It's a dual zone system, allowing driver and front seat passenger each to set their preferred temperature.

There are also controls for activating the rear compartment ventilation.

A host of safety systems, from anti-lock brakes to electronic stability control, are backed up by standard tyre pressure monitoring.

Now this sort of space and gracious luxury does not come cheap, with prices ranging from £38,470 to more than £51,000.

Auto facts Mercedes-Benz R 320 CDI L SE

  • Price: £42,970
  • Ins group: 19
  • Fuel consumption (Combined): 30.4mpg
  • Top speed: 134mph
  • Length: 515.7cm/203in
  • Width: 192.2cm/75.7in
  • Luggage capacity: 13.9 cu ft
  • Fuel tank capacity: 17.6 gallons/80 litres
  • CO2 emissions: 246g/km
  • Warranty: 3 years/unlimited mileage