But “university seemed too easy”, he says, and he was by nature an entrepreneur. He set up a window-cleaning business, hiring other people to do the work and keeping half the takings. In Germany, for example, children can be challenged hard, whereas in the US they give up with hardly a struggle. Japan, a market that Meccano is investigating, is the strangest because the children believe they have to build all the models as quickly as possible.His close attention to the juvenile psyche seems to be paying off. When he bought Meccano in 1989 it was turning over pounds 6m and employing 60 people.

It is more challenging than Lego and more satisfying than video games and he is convinced that children need a tangible balance to virtual play.There is a key, he says, to a successful construction toy: it must be difficult enough to challenge a child, but not so hard that he cannot complete it. This balance is difficult to judge, especially as the standards vary from country to country. It will never again be a mass toy, but he believes there is a kind of child – the patient kind – who will take to Meccano. A bespectacled eight-year-old is discussing a Meccano television advertisement he has just watched. “J’ai l’impression que c’est cool, c’est splendide, c’est extraordinaire,” he says. Mr Duvauchelle looks chuffed.He considers that, as president of the company, his main job is to get inside the minds of kids “I buy their music, their papers, their books,” he says.

In the process he has developed a theory to explain why Meccano can flourish in a world of instant gratification. He does not make trunnions just to please middle-aged Englishmen, of course. Mr Duvauchelle, who is still only 44 despite his grey-white hair, is a seriously successful businessman who is working hard to rebuild a battered brand. His over-riding interest is not in pleasing the confirmed hobbyist, but in recapturing the customer that almost escaped: the child.
At a market researcher’s office in western Paris we are staring intently through a two-way mirror. He runs Meccano SA from an office near the Bois de Boulogne in Paris, and at his factory in Calais 350 people churn out trunnions, contrate wheels and swivel bearings that recall a gentler age of short trousers and school caps. For he is owner and therefore guardian of the hallowed institution of Meccano. Yet the people who owe Mr Duvauchelle the greatest debt are British.