According to today's Financial Times, Britain is Germany’s fifth-biggest trading partner, with bilateral trade amounting to €122bn last year. Two thousand German companies have subsidiaries or branches in the UK, employing 370,000 people and accounting for €110bn of direct investment. Most of the goods they produce are destined for Europe, so the prospect of Britain leaving the EU single market and customs union has triggered real alarm. On the day after the Brexit vote in June 2016, the 30 groups listed on Germany’s DAX index lost €65bn in market value, according to the Handelsblatt newspaper.