The system works by using a normal internal combustion engine, special hydraulics and an adapted gearbox along with compressed air cylinders that store and release energy. This enables it to run on petrol or air, or a combination of the two.

Air power would be used solely for city use, automatically activated below 43mph and available for ‘60 to 80 per cent of the time in city driving’. By 2020, the cars could be achieving an average of 117 miles a gallon, the company predicts.