WHEN Bentley founder Walter Owen Bentley announced his automotive manufacturing venture in 1919, as Britain was shaking off the horrors of World War I and preparing to launch into the Roaring ’20s, he promised that all of his vehicles forthwith would be able to reach 100 miles per hour (161km/h).

We can hereby attest that Bentley’s latest addition, the Bentayga Diesel, is well up to the mark. May we quickly point out that this test of the big SUV’s straight-line prowess was achieved on a closed test road at a vehicle proving ground in Torquay, Victoria, and not on the Hume Highway.

But we will also let you in on a secret: at 160km/h, the accelerator pedal is still a l-o-o-o-o-n-g way from the floor. This would indicate that Bentley’s claim that the 4.0-litre V8 Bentayga Diesel is the world’s fastest diesel SUV – at 263km/h and 0-100km/h in 4.8 seconds – is probably in the ballpark.

If you want to go faster, there is always the 447kW 6.0-litre W12 petrol Bentayga flagship that manages 301km/h and 4.1s to 100km/h.

The W12 kicked off the Bentayga launch in Australia in mid-2016, with initial allocations all sold out, despite a pricetag of $427,300 plus on-road costs.

That’s all very impressive, but now we are getting down to the real Bentayga business: the Diesel.

This is the variant that will account for up to half of all Bentayga sales in Australia where diesel is king in large SUVs, especially those of the luxury type.

Apart from the fact that it is the cheapest Bentley in the current range, at $335,000, the Bentayga Diesel has the appeal of lazy torque, with all 900Nm arriving just above idle.

Just lean on the throttle and go, swept away on a creamy wave of barrel-chested torque.

And this is the thing about the Bentayga Diesel: just about everything about it has a certain laidback feel, like a relaxing weekend at an English country estate, even when the world is flashing past the side windows at unseemly haste.

During foot-to-the-floor acceleration or savage emergency braking, the Bentayga feels fully, quietly in control. And for a diesel, it is impressively quiet.

There’s no alarming pitch and roll on winding roads at speed, despite being a relatively tall vehicle with a reasonably high ride height. The active air suspension and big tyres keep things on a level plane, while at the same time riding bumps like a sumptuous, expensive luxury car, which, of course, the Bentayga is.

The driver can switch from comfort to sport mode (or custom settings, if the driver can be bothered) via a knob on the console to firm things up a bit more, but even this is not unduly taut, just faster.

Urban boulevards and glorious country roads are the natural habitat of vehicles such as this, but what if you really wanted to take your finely crafted $335,000 pride and joy off-road, say, through the back tracks of the Victorian High Country or for a gentle jaunt down the Birdsville Track?Of course, few drivers of any type of SUV, let alone those who would buy a top-end vehicle such as this, actually go venturing in the rough stuff, but they like to know they can.

On your behalf, we have given the Bentayga Diesel a short workout on the four-wheel-drive track at the aforementioned proving ground.

First up, we noticed with a tinge of alarm the lack of low-range gearing, meaning we would have to rely on the eight-speed automatic transmission and boundless torque to haul us out of tight spots. However, this particular car was equipped with an optional off-road pack that provides various electronically controlled traction modes for ice, mud, etc.

Truthfully, we did not go severe rock-hopping, but we did venture through mud and slush, door-deep water wading pools and up some steepish, deeply rutted slopes made more difficult by about 100mm of rain a couple of days before.

Through it all, the Bentayga did not miss a beat, virtually idling up the hills with all four paws working via a Torsen centre differential to maximise grip, and then down the other side on automatic hill-descent control. In one particularly slippery section, the vehicle slid sideways into the ruts, but progress was maintained.

In all, it was all pretty impressive. In fact, Bentayga engineers claim their car is superior to the Range Rover in off-road conditions, which is some boast.

We are not sure about that, but can assure potential buyers that if they do bump through the bush, they will do so in tremendous comfort. No bash and crash here.

Those air dampers absorb the lumps to provide an eerily serene ride, just as they do on the bitumen. In the burled-walnut-trimmed cabin, the occupants ensconced in soft leather-swathed quilted seats will have the most pleasant of journeys, especially those in the back of the four-seat variant with its pair of luxury electrically adjustable pews, complete with heating, cooling and multi-mode massage function.

The five-seat version with its three-person bench seat is less luxurious, but most people will still think it is pretty swish. Roomy, too.

Unfortunately, we did not get to check out the new seven-seater that debuts on the Bentayga Diesel, as Bentley did not have one at the media event.

A glance in the back of the other variants revealed heaps of luggage space, but no full-sized spare wheel, which might give off-roaders pause for thought.

But let’s face it – this is a high-riding ultra-luxury car, offering pretty much everything that opens and shuts. If we have not mentioned it by now, don’t worry – it is most likely there. And if it is not there, Bentley’s Mulliner craftsmen will be happy to supply (for a price).

Yes, it is expensive, but if you want what is arguably the best luxury SUV going around, the queue starts at Bentley’s five dealerships around Australia.