Donald Trump’s US election campaign threat to impose 10% levies on US trading partners could hurt the UK economy

Outside the US embassy in London, a steady line of visitors arrive for visa appointments. On the windswept south bank of the Thames, the fortress-like building is not the most welcoming proposition: it stands isolated, a cold glass cube hemmed in by a medieval-style moat.

Inside, after Donald Trump’s election victory last week, the atmosphere was not much warmer. Having flown in to promote US trade links with Britain, the governor of New Jersey, Phil Murphy, knew his job had just got a lot harder.