Bentley has unveiled the fastest four-seater soft-top in the world with its new 202mph Continental GT Speed Convertible.

Featuring a twin-turbo W12 engine tuned to produce an astonishing 616bhp, the convertible version of the GT Speed that was unveiled last year shares most of its technology with its hard-top sibling.

The engine has been improved in every respect, and despite packing 175kg of extra weight over the current hard top version the latest Convertible is still 15% more efficient than the first GT Speed was. The new 2.5-tonne flagship records 19.5mpg on the EU standard test cycle, with CO2 readings of 347g/km.

The efficiency gains amount to around a 15% increase in the car's range; an improvement that could increase further with steady cruising. Fuel tank capacity is 90 litres.

Top speed is down 3mph compared to the hard-top GT Speed, while the 0-62mph sprint is just 0.2 seconds slower. The hard-top hits 100mph 0.7 seconds faster, though.

Like its enclosed counterpart the GT Speed Convertible uses an eight-speed ZF automatic gearbox for incredibly fast, reliable and smooth changes both up and down. Paddles are present behind the steering wheel for semi-manual shifts if desired. It is also capable of `block-shifting', for example from eighth to fourth.

The famed Bentley `wave of torque' is maintained, with a monumental peak of 590lb.ft sustained between 2,000rpm and 5,000rpm.

The four-layer acoustic fabric hood is said to keep road noise to a minimum. During its development it was tested in temperatures from -30 to +50 degrees Celsius, with Bentley claiming it can withstand monsoon rain and maintain `draft-free warmth' even on the coldest winter days.

Handling improvements over the standard Continental GT Convertible come from stiffer suspension bushes and stronger anti-roll bars, while the ride is set up 10mm lower.

Prices have yet to be confirmed but are expected to sit around the £160,000 mark. As per the Bentley norm, the options list will be extensive and expensive.