The man presiding over this success is Dr Franz-Josef Paefgen, a German who was previously the head of Audi. His move to Bentley in 2002 looked like demotion - although he continued to head up the Volkswagen Group’s research and development and motor sport activities. But clearly he enjoys his life as an honorary Englishman and the results he has achieved with Bentley are there for all to see.

Bentley now has a six-model range – three variants of the Continental and three of the more expensive coachbuilt Arnage. But how far can the company expand production and still retain the marque’s exclusivity?

Paefgen: ‘That’s difficult to say but Porsche makes 100,000 cars a year and is still considered an exclusive sports car maker. The important thing is how they got there: they progressed step-by-step and were careful to preserve clear brand values.

‘We will not say no to further growth, especially with new markets like India and China developing so fast but with the current line-up of models we are where we want to be.’

Bentley cars and their engines are built in Britain but most of the components come from Germany. Paefgen says that will continue.

‘We are the biggest user of the Volkswagen 12-cylinder engine and so we have a lot of influence on what happens with this power plant. And the V8 engine (ex-Rolls-Royce) is still a unique selling point for the Arnage. We have no plans to stop the V8, which celebrates its 50th anniversary this year. We are very near to making it comply with 2009 Euro V exhaust emissions regulations.’

Many outsiders have suggested that Bentley should make a smaller and more economical car to reflect concerns about the environment and climate change. Paefgen rejects this idea. ‘We could sell a smaller car or an SUV but what would it do to the brand? At the moment I don’t think it’s the right way to go.’

Instead, Bentley has announced a plan to make the existing cars more acceptable to the environmentalists. It claims that, by 2012, Bentleys will be able to achieve a ‘well to wheel’ average of less than 120 g/km CO2. This astounding improvement is because all of its models will be flex-fuel and be able to use second generation bio-ethanol - made from bio-mass, waste material, rather than food crops.

But this is not quite what it seems. No-one else expresses CO2 figures this way and, measured at the tailpipe without considering the origin of the fuel, the reduction bio-fuel can achieve is from 465 g/km to about 400. The average family hatchback has a CO2 figure of around 160 g/km.

Of course the CO2 emissions attributable to Bentley are negligible in the greater scheme of things and they will be included in the Volkswagen Group’s tally for the forthcoming European Union regulations. The Bentley move is a gesture to show it is a good corporate citizen. Paefgen admits it is symbolic: ‘There was no pressure from owners or buyers and there is no legal requirement. But customers do expect us to give answers to the questions about harm to the environment.’

And it is looking longer term, to the next generation of cars that may be lighter and more efficient than today’s models but should not, Paefgen believes, be smaller, or have less performance. ‘Our customers want cars to continue in the current size and style.’

He promises a big step in 2012 - a power plant with the same torque and power as Bentley’s existing engines but with a 40 per cent CO2 improvement. He won’t say whether it will be a diesel or a hybrid but that may be because it will be both; on their own, neither system would achieve that degree of improvement.

The 6.0 litre V12 diesel now available in the Audi Q7 – and showcased by the R8 TDI Le Mans – could be combined with the hybrid system that Porsche has developed with Volkswagen for SUVs to make a Bentley the greenest prestige car in the business.

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