The days of driving flat out through the wonderful French autoroute system are over. We try a 21st-century solution combining luxury, economy, and tonic for the soul.

Car-folk like to wax lyrical about the German autobahn system, mainly because it’s still the only highway system in Europe which, in parts, has no speed limits. I remember when headed, excitedly, for my first trans-German journey in a fast car, dreaming of empty roads where you could go as fast as you damn-well pleased…only to be greeted by traffic jams and crowded carriageways from the Dutch border through to Austria. Nobody mentioned the other cars.

At that time, a decade or two ago, France, not Germany, was automotive nirvana. The French autoroute system, being mainly private, toll roads, was beautifully engineered, with velvet smooth tarmac, wide lanes and precious little traffic in many parts. There were speed limits, but seemingly nobody to enforce them: the gendarmes were all more interested in hassling Algerian immigrants, or eating cassoulet, or whatever it was they did.

Then, something happened. A few years back, President Chirac decided that, having not achieved very much at all during his years in power, he would crack down on drivers. The sleepy gendarmes in their claptrap Renault Fours mutated at scarily rapid pace into a Gallic Highway Patrol. On-the-spot fines were imposed, and if you went fast enough - all too easy as the roads were still smooth and empty - your car was impounded. Since then many a car owner has returned to England by train, sans car and licence.

So this year I decided to travel the autoroute system again, en route to Provence, but in a different style. I’d travel in luxury rather than at speed. I loaded my Valextra luggage into the Mercedes S 320 CDI, and aimed for the Channel Tunnel.

I think of this every time I climb onboard my Mercedes S class. Having driven pretty much every luxury car of consequence in the world today, I can safely say that none, including the S class’s big cousin, the Maybach, feels as expensively puttogether. Everything you touch, from the wood and leather steering wheel, to the metal (not plastic) switches for the ventilation and lights, to the bit of the door your hand rests naturally on, feels classy.

Some things haven’t changed: the sudden jump in quality of road surface and design on the French side is still striking. Roads are smooth, lanes wide, cambers are beautifully done (and there are no roadworks - how do they do that?). The S Class settled into a hushed, smooth, soothing cruise at a police-safe 90 mph (145 km/h). Haydn wafted out of the sound system; the super-soft headrest (really like a leather pillow) caressed my head, and I was in Reims, champagne country, before I really knew it. Is it really this nice driving less fast?

The other surprise: cruising with the superefficient diesel engine purring along barely uses fuel. It was Burgundy before I had to fill up, more than 500 km from London.

While the A26 motorway, which connects Calais and Burgundy is new and easy on the traffic, the A6/A7 motorway, which it merges with in Burgundy, is a main artery and was positively Brit/German in its traffic levels. This is where I was delighted to have two things in the Mercedes: the instant pull of the torquey engine, and the fabulous safety system which beeps if you’re too close to the car in front and actually brakes for you if you get too close. It also prepares your seat belts and other safety systems for the crash if it’s about to happen.

I arrived in Provence with a smile on my face, after what had been an utterly effortless journey. How much difference had my restrained speed had? Er, almost none at all - the frugality of the S320 meant I hadn’t had to stop for fuel, so I actually saved time, fuel, and stress. Vive La France and ex-President Chirac; and my truly effortless car. – Darius Sanai

Mercedes-Benz S320 CDI; Mercedes.co.uk