As the owner of a Nissan Leaf, one thing is certain - you won’t be doing any long journeys. So when I needed to head up to Lancashire, via the south Midlands, back to London and then straight up to Stansted airport, I needed an internal combustion engine.

Editor-in-chief Steve Cropley kindly lent me the keys to his Mercedes S350 Bluetec, which comes equipped with an impressive V6 diesel engine and a very big fuel tank.

I headed up towards Stratford on a Saturday evening from the southern end of the M40 and was amused to, as the traffic started to thin out, the Merc flashed up an amber warning that the car had just 75 miles range left, which is more than the Leaf usually has after a day’s commuting.

I filled the car at Oxford services. It swallowed £108 of diesel. However, as I cruised back up the empty M40 at an indicated 80mph, the trip computer’s predicted range was steady rising. From a 550-mile range after filling up, the distance-to-empty steadily rose to 670 miles, suggesting I might have discovered perpetual motion.

The S350 has clearly been optimised for the 80mph autobahn cruise. The dash has a scrolling horizontal bar showing instantaneous fuel consumption. Hit the right speed and throttle opening and the bar shoots rightwards, up to the 40mpg limit.

Which is an odd piece of programming by Merc’s instrument specialists because when this car is in the zone, it’s clearly good for over 40mpg. Maybe, way back when this W221 programme began, nobody would have guessed that a 40mpg+ S-class was possible.

True, the impressive economy takes a serious hit in heavy urban traffic, but there’s a good chance I could drive from central London to Lake Geneva and still have 100-mile range on the dash. And that’s another thing about this car.

The super-fat, super-wide, seats, the tall tyres and the isolating suspension may mean it is a completely uninvolving drive. But the other side of the calculation is that this car has a remarkable ability to cover ground without the driver much noticing.

My standard long-distance lope is from J28 of the M6 to the end of the M1 - a distance of 210 miles. The S350 broke all records, admittedly on a reasonably quiet run, demolishing the distance quicker than any other car I can remember and, more importantly, it was such a relaxed experience that jumping out of bed the following morning and heading for Stansted was easy.

After spending the best part of year in an XJ, I have to admit that driving through the seat of your pants is not the only way forward. The S-class sort of disappears around you, but it makes for a remarkably effective way of covering big distances.