Developed as a rival to the Mercedes-Benz SLS E-CELL, the rear-wheel drive coupe uses a T-shaped battery pack housed in what would normally be the central transmission tunnel and behind the seats, supplying independent 140kW motors on the rear axle.

The R8 e-tron was claimed to pass 62mph in 4.6 seconds with a theoretical top speed of 160mph, but the cars have been limited to 126mph to boost efficiency. A range of between 110 and 135 miles was claimed, depending on driving style, and the car set a lap record for series-produced electric vehicles at the Nürburgring Nordschleife in Germany – completing the 12.92-mile circuit only four seconds slower than the V8 petrol version.

Wolfgang Durheimer, head of research and development at Audi, explained: ‘At the moment I don't see an economically interesting business case with the price and the energy density we would be able to deliver [with current battery technology].

‘Each car costs us €1 million. It cannot be subsidised by the customers for our existing vehicles and we are not willing to lose money selling it. But the R8 e-tron is a showcase for what is possible, and our findings from developing it will find their way into all future Audi applications of e-mobility.’

Just 10 R8 e-trons have been built, and their future is likely to be as museum pieces after a further test programme. ‘We are not allowed to sell them, so ownership will have to remain with Audi,’ said one company insider.

All of the 10 that have been made are showroom-ready, with the refinement, operational smoothness and attention to detail that's become synonymous with Audi. Sadly, only company insiders will now ever get to find this out for themselves.

The first volume production model to be badged e-tron will now be the A3 Sportback, which will feature a petrol-electric plug-in hybrid drivetrain. Sales will begin by the end of 2013.