Bentley Mulsanne exclusive

Bentley's new Mulsanne is undergoing final testing around the world as the British marque prepares to launch its Rolls-Royce Ghost rival.

Autocar's Greg Kable joined the development team in the old mining town of Kimberley in South Africa, as they put the Mulsanne through hot-weather and dust testing.

When we meet up in Kimberley, Bentley’s engineering team has already spent a good part of the previous week out on the road, putting miles on the Mulsanne. In a bid to gauge the level of progress, two prototypes have been flown in from England; one reflects where the Mulsanne’s engineering was at a year ago and the other has all the very latest developments planned for the production version.

It’s already late in the day when we meet the team, so we waste little time in hitting the road. The test procedure today involves driving at legal speeds with a stop every 30 miles or so, at which everyone swaps seats. This way I get to experience the Mulsanne from the front and (importantly, given that most buyers will be chauffeured) the rear.

Not far from Kimberley there’s a long and straight gravel road covered in a thick layer of fine dust. It’s hardly where you expect to see a limousine performing full-bore getaways before running up to typical British motorway speeds and then backing off. However, it proves perfect for testing the rubber seals Bentley has chosen for the Mulsanne’s huge doors.

The next day, under bright blue skies, we head out of Kimberley again for a variety of different tests, including some sustained high-speed runs on surprisingly well maintained bitumen roads. Before we set off, though, there’s a 10-minute briefing to detail the day’s activities and focus attention on a report placed in each of the Mulsanne prototypes.

The first entry into the report is made by Bentley's engineering boss Ulrich Eichhorn even before a wheel is turned. He’s concerned about the ride height on one of the prototypes. “It needs to drop by 5mm,” he says pointing to the space between the Mulsanne’s towering 21-inch wheel and the top edge of the front wheel arch. “It’s not a big problem, it’s just a software fix.”

For the next four hours we pound across the vast reaches of South Africa at speeds of up to 160mph. The Mulsanne devours big distances at high speed with terrific composure and astonishing refinement. There’s an alluring burble to the engine, but it’s always distant and never grows to more than a hushed hum.

When we arrive at a service station to refuel, the digital gauge within the newer of the two Mulsanne prototypes’ instrument binnacles is showing 34deg C – hardly the sort of broiling conditions I expected for a hot-weather test of Crewe’s latest saloon. But as part of its testing procedure, Bentley has already exposed an early example of its new upper luxury saloon to more than a year of sunlight somewhere out in the South African countryside.