It just didn’t add up. The Volkswagens were spewing harmful exhaust when testers drove them on the road. In the lab, they were fine. Discrepancies in the European tests on the diesel models of the VW Passat, the VW Jetta and the BMW X5 last year gave Peter Mock an idea.

Volkswagen boss Martin Winterkorn says he is stepping down over the diesel emissions scandal, but insists he's done nothing wrong.

Volkswagen CEO Martin Winterkorn says he is stepping down “in the interests of the company” as it grapples with the emissions scandal.

Martin Winterkorn’s days as head of Volkswagen appeared numbered yesterday after the German car maker said a scandal over falsified vehicle emission tests in the US could affect 11m of its cars worldwide.