In the last days before the European referendum I appeared on the BBC with the Brexit campaigner Andrea Leadsom. I expressed my concern that, because of the terms we would secure, our trade with Europe would suffer if we left the EU. Ms Leadsom was convinced I was wrong.

She patiently explained that German car manufacturers and other European businesses would not allow their political leaders to damage trade with Britain in order to pursue political objectives. We would get smooth, tariff-free trade. European leaders would not — could not — afford to ignore companies like that.

Equally patiently, I put the counter view. Even if Mercedes-Benz acted as she supposed, which I wasn’t sure they would, why did she believe it would work? Big