Range Rover’s new flagship diesel version will be the first production car to have a special system built in to prevent drivers filling the tank with petrol instead of diesel.

With modern diesel cars behaving more like petrol-powered vehicles than ever before – and more drivers making the switch to diesel – many are being caught out at the pump. Motoring recovery groups have reported a sharp increase in call-outs due to this problem, and it seems that writing the word DIESEL in great big letters on the filler cap just isn’t doing the job.

The Range Rover TDV8 now has a petrol fuel guard system incorporated into the vehicle's diesel filler head that automatically activates a mechanical shutter if a petrol nozzle is inserted. Rather simply, the system distinguishes between petrol and diesel nozzles because thinner unleaded petrol dispensers go deeper down the neck of the vehicle's fuel tank, thus activating the shutter.

The AA reported that in 2005, more than 100,000 cases of mis-fuelling were reported, with diesel vehicles being filled with petrol in error. The associated costs are significant, often amounting to several thousand pounds if the incorrect fuel enters the engine during ignition.