We have reached peak SUV. Behold the 2019 Rolls-Royce Cullinan, the most expensive and most lavishly appointed off-road-capable vehicle ever built. That's right. The Cullinan is no louche boulevardier: Press the button on the center console labeled Off-Road, and the big Rolls will lift its skirts and ready itself for rough tracks, gravel, wet grass, mud, snow, sand, and water up to 21 inches deep. But it will also do 155 mph on the autobahn. And all the time those inside will be riding in the lap of luxury.

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The Cullinan has been a long time coming, and despite the coy references to it being a "high-bodied car" during the development program, even Rolls-Royce's own press materials refer to it as an SUV. Like Lamborghini's Urus, the $325,000 Cullinan redraws the boundaries of the world's most dynamic vehicle segment. And then some: Rolls-Royce North America sources expect that with options, most Cullinans arriving in the U.S. from early 2019 will have cost their new owners at least $400,000.

Improbably, perhaps, Rolls-Royce has genuine off-road credentials. Back in the early 20th century, when few roads outside major metropolitan areas were sealed, the superbly engineered Rolls-Royce cars developed a reputation for reliability and durability in extreme conditions. Maharajas in India drove Rolls-Royces along rough, dusty dirt tracks; so did wealthy sheep farmers in Australia. Lawrence of Arabia commanded a fleet of nine Rolls-Royces in the Sinai Desert during World War I, six of them bodied as armored cars.

The Cullinan is built on what Rolls-Royce calls the "Architecture of Luxury," a flexible, aluminum-intensive space frame architecture that made its debut with the Phantom VIII last year and has been designed to eventually underpin every future Rolls-Royce, including the replacements for the Ghost, Dawn, and Wraith. Under the hood is the 6.75-liter twin-turbo V-12 shared with the Phantom but tweaked to deliver a velvety 563 hp at 5,000 rpm and a stout 627 lb-ft of torque at just 1,600 rpm.

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The engine drives all four wheels—Cullinan is the first 4WD Rolls-Royce in history—through an eight-speed automatic transmission and a drivetrain similar in concept to BMW's xDrive but designed and engineered to handle the Cullinan's industrial-strength power and torque outputs. The height-adjustable multilink suspension is also unique to Cullinan, with larger air springs to handle the car's 5,864-pound mass and to better absorb impacts off-road. Rear-wheel steering helps improve agility on winding roads.

The Cullinan has a majestic presence, though in photographs devoid of street furniture and other vehicles, it doesn't look quite as imposing as expected. Even up close and personal—we were given a sneak peek at the Rolls-Royce factory at Goodwood a few weeks ago—it's difficult to comprehend how big the Cullinan is, a tribute to the confident, precisely proportioned sheetmetal styled under the direction of Rolls-Royce design director Giles Taylor.

At 210.3 inches, the Cullinan is a quarter inch longer overall than a Lincoln Navigator and 2 inches lower, and it rides on a 129.7-inch wheelbase that's a massive 7.2 inches longer than the big Lincoln's. From the front, there's no mistaking it's a Rolls-Royce. That famous grille stands proud, well forward of the headlights and fenders. The bustle tail—a nod to the trunks literally strapped to the rear of Rolls-Royces in the 1920s—and an elegant sedanlike C-pillar give the Cullinan a more carlike demeanor than regular two-box SUVs.

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See all 38 photos

The low beltline and airy glasshouse add visual lightness to the Cullinan's side profile. And in conjunction with the glass panorama roof, they help flood the Cullinan's cabin with photons, too. You ride high, wide, and handsome, no matter where you're sitting. It's an old cliché that the best place to experience a Rolls-Royce is from the back seat, and the Cullinan keeps it alive. The large rear doors are hinged at the rear and open wide, making entry and egress easy. The rear passenger H-point is higher than that of the front passengers to enhance outward visibility, and there's a ton of legroom.

Two rear seat configurations will be available. The standard Lounge Seat setup offers room for three, and the seats fold flat, a first for Rolls-Royce. The optional Individual Seat configuration features two fully adjustable seats separated by a fixed console that includes a drinks cabinet with Rolls-Royce whiskey glasses and decanter, Champagne flutes, and a fridge to keep your favorite Dom Pérignon chilled.

It's an SUV, so it has to be practical, even if it is a Rolls-Royce. In cars with the Lounge Seat configuration, the split tailgate opens wide to reveal 43.4 cubic feet of load space that expands to 68.2 cubic feet with the seats folded flat. The leading edge of the rear load space floor can be moved up at the touch of a button to provide a smooth floor for objects almost 7.5 feet long. Customers who opt for the sybaritic comfort of the Individual Seat setup are judged not to be the load carrying type: The seats are fixed, and there's a glass panel immediately behind them to prevent expensive hairdos being ruffled by hot desert gusts or icy blasts when the tailgate is open.

"A Rolls in the desert is above rubies," Lawrence of Arabia once said. The Rolls-Royce Cullinan is named after the largest diamond ever discovered, now part of the British Crown Jewels. A Freudian slip? Hardly. In terms of its potential contribution to the bottom line, the Cullinan is probably one of the most valuable vehicles Rolls-Royce has ever launched.

See all 38 photos

See all 38 photos