Bentley’s new Continental Supersports Convertible will be the fastest and most powerful open-top Bentley ever when it goes on sale in June.

Supersports models are the most extreme interpretations of the Continental — hence the name, which was made famous by 1925’s Bentley Supersports, the fastest and most powerful car of its day.

The Supersports Convertible’s twin-turbocharged W12 engine produces 621bhp and 81kgm of torque. It takes 3.9sec to get from 0-100kph and 9.6sec to reach 160kph from a standstill, and can reach a top speed of 325kph.

Power is sent to all four wheels through a six-speed ZF Quickshift automatic gearbox, which cuts shift times to just 93 milliseconds and allows double downshifts.

As in last year’s Supersports coupé, Bentley has reduced the weight of the four-seat Supersports Convertible over the standard car. Almost 100kg has been shaved off the base car’s 2485kg kerb weight, through the use of lightweight 20-inch alloys, carbon-ceramic brakes, lightweight seats and carbonfibre in its cabin.

The Supersports Convertible is the latest Bentley to receive the firm’s FlexFuel technology, which allows it to run on petrol, E85 biofuel or any mix of the two. Bentley says FlexFuel cuts ‘well to wheel’ emissions by 70 per cent and the technology will be standard across the Continental range from the 2011 model year.

Bentley has revised spring, damper and steering settings, and the four-wheel drive system has a 40/60 rear-biased torque split to cut understeer. The rear wheel arches have been flared to accommodate a 50mm increase in rear track, and the ESP has been tweaked to intervene less at low speeds.