Two years ago, the American business community made a Faustian bargain with Donald Trump: give us tax cuts, and we will support your administration. Now the US president is having his due. His trade war with China has turned into what looks to be a serious and possibly permanent breakdown in relations between the world’s superpowers. Tariffs have turned into retaliatory tariffs. Supply chains are shifting. Markets are turning. Within all this change, multinational companies, which have arguably been the biggest financial beneficiaries of globalisation since the second world war, have the most to lose.

Business has complained for decades about Chinese theft of intellectual property and the difficulties of obtaining equal market access in the Middle Kingdom. These are legitimate complaints. Yet when push came to shove, few American companies were ever willing to speak out in public about what they viewed as unfair terms of trade for fear of losing access to the Chinese market.

Now global companies and their shareholders are being hit hard by an increasingly dangerous trade war. It is a conflict started by a president who makes little distinction between legitimate complaints about Chinese mercantilism, and irrational demands, such as expecting Beijing to shift its entire economic system and rewrite its laws to suit the US. Mr Trump is even willing to punish not just adversaries but allies such as the EU, Canada and Mexico, turning tariffs into a weapon to be deployed around completely unrelated issues, such as immigration.