The moustache has its uses, though. It sells cars.

Capitalising on his time running the Chrysler/Jeep bit of the empire over in Detroit, for which success he was rewarded with the group, Zetsche has recently appeared in a number of entertaining television ads in America as "Dr Z", where his fluent English with a noticeable German accent trumpets the benefits of the American firm's links to Teutonic engineering traditions.

In one he drives a Jeep round a test track. When asked by a journalist whether he is "really a doctor" he piles the Jeep into a concrete block. Obviously the Jeep's excellent safety features see both men walking from the wreck intact, Dr Z with a smile.

Dr Z even has a website devoted to him ("Ask Dr Z").

By the way, he really is a doctor, having completed his doctorate in engineering at the Technical University of Paderborn. He's been at the group since 1976.

10am Despite the cult of personality he seems to have developed in north America, over here Dr Z's minders are intent on keeping the company's media coverage focused on cars rather than big 'taches. Even so Dr Z was prepared to let slip that he was involved for much the day in "boring meetings" about corporate plans.

I think he was being rather tongue-in-cheek, as he often is. Even so, corporate plans take up a good deal of his time. The company is vast and complex, though slightly less so than it was. Previous attempts at diversification by the group away from car making, into domestic appliances and aerospace, have been largely unwound.

(Though they still hold a 22.5% stake in the troubled EADS combine. ) Today DaimlerChrysler is about making cars: lots of them. It's the world's fifthbiggest auto maker and it encompasses Smart, Mercedes-Benz, Maybach, Jeep, Chrysler and Dodge. Plus the van and trucks businesses.

They've been disengaging themselves from former alliances with Mitsubishi and Hyundai (though links remain). But the era of complexity and adventurism went with Dr Zetsche's predecessors: Jurgen Schrempp, who Dr Zetsche supplanted at the start of this year, and Edzard Reuter, who was ousted by Schrempp in 1995.

With quality issues at Mercedes-Benz, and the problems of rationalising the American and German brands, plus continuing losses at Chrysler and Smart, there is plenty to occupy this clever Doktor's mind. They're making the final preparations for the launch of the new Cclass saloon, due to be unveiled on 18 January, a truly vital car.

Today, it's Smart's turn to begin to steer itself into financial viability with the "unveil" of the new Smart city car, the ForTwo. It's the last remaining Smart model, the roadster and ForFour hatch having been canned.

They've made about 750,000 of the old car since 1998. With the new model - safer, more powerful and bigger - Dr Zetsche has high hopes for a success in the US, where the Smart hasn't yet been seen: "Given the higher cost of gas and increasing traffic congestion, the time is right for Smart - 40 plus miles per gallon and a 400mile range. The 'it' car in Europe can become the 'it' car in America." They're hoping it will land in the big American cities in 2008.

3pm You get the impression that Dr Z would be much more happy on the road. His everyday transport is a MercedesBenz S-class and a Smart.

He's fond of the marque, having had something to do with its inception in the 1990s while he was chief engineer of the cars development division. (In those days Dr Z was a three-piece-suit man, though he's always had the face fungus. ) He acknowledges that they tried to expand the Smart brand too quickly: "We were moving too fast on an expansion mode before building a solid base. We will not repeat that mistake. We'll stay with ForTwo for the time being and have a base that will allow it to be profitable and economically feasible."

But it's not all about money.

Dr Zetsche enjoyed his test drive in the new Smart ("where the fun is!"). He piloted the Smart over the Alps, chasing a 3.5 litre V6 car all the way, with the only proviso that they all stuck to the speed limit.

The route took them from Turin to Nice, and all the way up to 2,800 metres. "Driving in the Smart behind this large car I thought 'bye, see you tomorrow', but it was almost bumper-to-bumper. It was not a race but it was a very dynamic drive. We didn't set any land speed records, however the ForTwo was well up to the task."

8pm DaimlerChrysler has taken over a car park in Stuttgart and built a sort of nightclub on its roof, with sufficient drink and canapes to sate the appetites of the 700 or so journalists bussed, driven and flown in from all over.

The affair is very "new Germany", self-consciously youthful, funky and avantgarde. Even with Nikki Lauda around, Dr Z is of course the main star of the show.

The Great Moustache dominated the space, indeed the whole of Stuttgart. The following gives you an idea of Dr Z's sense of humour : "I trust we gave you some notso-subtle reminders of the benefits of the Smart on your drive up, as expressed by Smart cars and exhibits on Smart owners' lifestyles. I personally thought the displays were 'smart', fun and innocent.

That was until I heard an alternative interpretation of the display down on level 3. It shows how two Smart ForTwo cars fit into one parking space and that two conventional cars can only do so if stacked one on top of the other. Someone, who will remain nameless, said that scene might suggest an act of 'extreme affection'. Now I can assure you that that was not our intent - although one possible exception could be that our next-generation Smart brings out the love in both man and machine."

Cheesy or what? Maybe we should be grateful though.

When he launched the Dodge Charger he wore a Stetson and at the Frankfurt show he arrived in a Jeep wearing a leather jacket and a baseball cap. He is a sort of human American-German merger himself. Perhaps.

9pm After the presentation and photo call with the new car, just about every hack in the hall descends on Dr Zetsche.

He's clearly used to the attention, though, and spends another hour or more taking to journalists. Even when he's trying to relax over a glass of beer and grab a plateful of risotto he gets little peace.

He repeats the same lines like a mantra, saying over and over again that the Smart line will be profitable, that it is a unique concept, that it is the car for now, how great its fuel consumption is and how much fun it is. Fun, even in such circumstances, is clearly the leitmotif of Dr Z's life.

10.30pm Dr Z leaves the building and returns to his family (he's married, to Gisela, and has three children: Two boys (21, 20) and a girl (18). I wonder if that moustache tickles?