They're all equipped with ECO-Start. It stops the engine when the vehicle is stationary — at the traffic lights for instance — for more than two seconds, then starts it again when the driver depresses the clutch pedal.

An early version of the system tested by journalists produced fuel savings of more than 10 per cent over a standard Sprinter. Available on all new Sprinters with four-cylinder engines and manual gearboxes, ECO-Start cuts harmful exhaust emissions too.

It costs £155, but the need for an up-rated battery and alternator boosts the total bill to £545.

One early adopter is Brighouse, West Yorkshire based roofing and building maintenance company Ploughcroft. It's acquired three medium-length high-roof Sprinter 209CDI vans equipped with the system through Bradford dealer Northside Truck & Van.

“We're already achieving a 10 per cent reduction in fuel costs compared with the non-Mercedes vans they've replaced,” says managing director, Chris Hopkins.