Bentley has unveiled its new open-top performance flagship -- and what it says is the world's fastest four-seat convertible -- which will make its official debut at the Detroit auto show later this month.

The new GT Speed Convertible "combines the sensory pleasures of roof-down luxury touring with the shattering performance of a 616hp, twin-turbocharged 6.0-liter W12, while delivering a 15 percent improvement in fuel efficiency," Bentley says. The car also features a close-ratio 8-speed transmission, uprated and lowered suspension and retuned steering provide exhilarating acceleration and sharp, communicative handling without detriment to ride comfort. Permanent all-wheel drive ensures optimum traction and power delivery whatever the road conditions.

Taking its place at the pinnacle of the Bentley Continental range, the new GT Speed Convertible has a top speed of 202mph and has a 0-60mph time of 4.1sec.

Subtle sporting design cues include exclusive 21-inch alloy wheels, dark-tint grilles and "rifled" exhaust tail pipes. Inside its handcrafted cabin, the GT Speed convertible features the Mulliner Driving Specification as standard, with its characteristic quilted diamond pattern leather, along with dark aluminum across the dash. Carbon fiber is an option.