"We're not just talking with Daimler about engines, we're talking about everything," Marchionne told reporters.

That quote, to be found on the Reuters website yesterday, is something that three years ago would have sounded like the wildest fantasy.

In June Sergio Marchionne, chief executive of Fiat Auto, signed a 2.4-billion Euro deal to supply Daimler with truck engines. Now he says that his company is bunkered down with the boys from Mercedes looking at how the two companies can further work together.

On one hand it shows the exceptional resurgence of a company that had a near-death experience a few years ago. On the other hand, it’s also a total mystery. Because why does Mercedes – having just untangled itself from a disastrous 10-year marriage with Chrysler – want to get back in the dating game with a volume car-maker?

We know that Mercedes cannot make decent profits from its uniquely engineered A- and B-class cars. The car’s tilted drivetrains are especially expensive to build. Buying Fiat engines – which are well regarded – makes sense. But taking the next step and perhaps sharing the next-generation Fiat Grande Punto platform looks like a risky step. The average punter would soon get the message that the new family of baby Mercs ‘are just Fiats underneath’.