Bentley has achieved record sales and profits on the back of its Continental GT and Flying Spur models but that doesn’t mean it’s forgotten its flagship Arnage, which is set to be replaced in 2010 by an all-new model. The car is starting to show its age against modern ultra-luxury rivals like the Rolls Royce Phantom and Maybach saloons but testing of the new model is well underway outside the carmaker’s headquarters in Crewe, England.

The new model will be based off a heavily revised version of Audi’s modular platform used for a host of models ranging from the A4 sedan up to the next A8 flagship. However, the Arnage will feature its own unique powertrain and will be strictly RWD. There are rumors Bentley may introduce a new diesel engine in the next Arnage range but the engine option is most likely to be a petrol unit.

Bentley also has a number of options in the Volkswagen Group parts bin, including both V10 and V12 units, and we could also see a new seven-speed dual clutch gearbox also appear in the new model. A high-performance Arnage T is also in the works but don’t expect it to feature the Bugatti Veyron’s W16 engine as previously rumored.

AutoExpress has posted a couple of spy images of an Arnage prototype, revealing a number of important clues about the future model. The extra-wide B-pillar indicates a longer wheelbase for the 2010 model and a slightly wider track should ensure a more dynamic drive than the current car.