DESPITE its extensive contours, the muscular Infiniti M model manages to look surprisingly gracious.

The posh brand from Nissan is becoming more easily identified on the UK motoring scene and the M version will only serve to increase that recognition.

It is still a small player in the executive premium saloon sector but these are early days and more dealerships are springing up around the country.

The Infiniti M's large, coupe-like architecture presents the image of a small limo. It looks good from all angles, though some aspects of the design are a little dated.

Its impressive profile and quality presentation make it a serious challenger in the executive market dominated by German marques - as well as the Jaguar XF and Lexus.

First impressions are that it is quite different to rivals, yet not drastically so. The lines are distinct and convey style and class.

On looks, quality build and luxury touches, the Infiniti M - in this instance powered by a 3.0-litre V6 diesel engine - shows lots of promise. And there's a good deal of muscle and pulling power to commend it as well.

The very competent M30d oil burner, also used in the Nissan Pathfinder, works well in propelling the M to 62mph in 6.9 seconds and on to a top speed of 155mph.

It glides swiftly and smoothly and relatively quietly in cruise mode, though the diesel decibels are more noticeable in town and city.

You do get the sense you are driving a hefty car - though the steering makes light work of urban driving and manoeuvres. It beefs up - though not enough at higher speed - so you don't quite get the feedback you would expect.

The seven-speed automatic transmission was reasonably smooth but changes are not as swift as you'd like, while the handling does feel a little heavy.

Driver and passenger comfort is assured, cosseted in a massive, luxury cabin that oozes class, wrapped in yards of leather. The ride, too, is beautifully pampered and the whole driving/riding experience is limousine class.

The M30d - with its considerable weight - isn't as thirsty as you'd fear with a combined figure of 37.7mpg. During one part of the test this plummeted to 18/19mpg admittedly in mainly stop-start short journeys. However, it recovered to return a more acceptable average of 28.5mpg.

The standard equipment list on the GT-trimmed test car is long and impressive and includes blind-spot monitoring, rear parking camera, automatic headlights, touch-screen sat-nav, 16-speaker Bose sound system, automatic braking and unintended lane-departure steering correction.

The Infiniti M's trump car is its individual styling. Whether that's enough to win over fans from BMW, Mercedes and Jaguar remains to be seen.

IF you are in  the market for an executive saloon, it's unlikely that the Infiniti M30d will be on your list, never mind the top of it.

In fact, Infiniti is probably the premium car maker you've never heard of -  unless you have spent a lot of time across the Atlantic.

In America the marque is as well-known as Mercedes and BMW are in the UK, but it probably has more in common with fellow Japanese brand Lexus.

It's a shame because the coupe-like M30 is a great looking car that performs flawlessly, is well specified, and is very pleasurable to drive. Maybe even the best car you've never heard of.

Infiniti is Nissan's luxury brand in the same way Lexus is to Toyota.

The Infiniti comes as the M30d diesel, the M37  petrol or the M35h petrol/electric hybrid. On test was the diesel in GT Premium trim and it's very, very good.

It has a powerful engine, a muscular rounded appearance that may not be everyone's cup of tea, and a high specification that marks the M cars out as serious contenders in the executive sector.

The large grille and dated rear end look a bit clumsy but one thing's certain, the M30 is a big car - a fact that's obvious inside the cabin.

It gives you a real feeling of size, cosseted in leather, heated and powered seats and an attractive fascia that is as clear as it is big.

Both front seats have electric adjustment for height, reach, angle and lumbar support and the steering wheel has electrically adjusted reach.

It is relatively easy to find a comfortable driving position, generous rear seat space doesn't mean you sacrifice load space, the boot is more than ample with 450 litres of spaceand a ski hatch allows longer loads to be carried.

The test car's 238bhp 3.0-litre turbodiesel engine produces a whopping 406lb/ft of torque and 199g/km of CO2 - good for a big, powerful vehicle that can reach 62mph in 6.9 seconds. Top speed is limited to 155mph.

The diesel engined GT is very much the ultra-quiet, smooth riding motorway cruiser. Great for the passenger but - lacking much feeling of precision or responsiveness - a bit boring for the driver.

Power delivery was effortless but it meant the manual shift paddles were redundant. It's far better to leave the car to sort itself out although the seven-speed automatic gearbox meant there were sometimes too many gear changes, not all of them smooth.

A drive mode selector allows you to move between normal, eco, sport and snow modes. Fuel consumption isn't the most frugal but for such a big car an average of 37.7mpg isn't too bad.