BIG saloons are having a hard time of it. Hardly surprising really as small and mid-sized models are getting quieter, more refined and speedier.

The rarefied territory of a luxury five-seater with hushed engine and cosseting hide upholstery is being encroached upon by a whole bunch of upstarts from the class below.

What's more, many potential buyers are tempted into generously proportioned SUVs which offer the same sort of boardroom ambience as the traditional prestige four -door.

All of which means that only the very best of breed are fit to survive in this super competitive market place.

Which brings me to the latest BMW 7 Series which, in the past, has tended to live in the shadow of the superb Mercedes S-Class.

But now the ball game could be changing. The new 7 Series was launched last year and immediately established itself as not only impressively refined, but one of the cheapest large saloons to run thanks to its efficient engines.

In this sector, the efficiency factor is probably of more significane to purchasers than the actual fiscal saving.

I drove the 740d version, the topline diesel which pumps out a generous 315bhp but has an appetite for fuel smaller than the average family five-door petrol powered hatch.

Instead of a 4.0-litre engine - as the 740 designation might imply - it packs a 3.0-litre twin-power turbocharged six-cylinder unit.

While there's no denying its girth and size, behind the exquisitely leather trimmed steering wheel the 740d feels a much smaller, more nimble number.

Despite the not inconsiderable power, it's easy to handle with a confident athleticism that's usually absent in luxury saloons.

Ride via air suspension is smooth and well damped with just moderate roll and the steering, though a tad numb, is precise with a sharp enough turn-in and sporty, close ratio rack.

Sport setting tightens things up nicely and emphasises the feeling that is no marsh-mallow limo. But with such an innate dynamic ability, keen drivers are left wanting still more...

With oodles of power available via an excellent eight-speed automatic gearbox, the large five-seater polishes off the dash to 62mph in a brisk 5.2 seconds. Top speed is an electronically restricted 155mph.

Best of all is the reserves of torque - 502lb/ft - which make easy work of overtaking.

The 740d comes with XDrive four wheel drive which further adds to cornering stability, especially in damp or slippery conditions.

Most of the time, the driver is simply unaware of the additional driving axle, but the system guarantees all the power transfers to the road surface without any drama.

Despite the abundant power, and a temptation to use it, economy is impressive.

It clocks up an official 55.4mpg with emissions of 134g/km. Even driven hard, I managed around the 40mpg mark.

Not only is the 740d loaded with kit - night vision cameras, four zone climate control and navigation, but the cabin surfaces are all leather trimmed.

There's ample leg and shoulder room all round, and if you want still more space, a long wheelbase model is available.

The latest 740d makes a strong case for itself in terms of refinement, driver enjoyment and even efficient running.