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.