Donald Trump promised “Brexit times 50”, and it looks like he was right. In a bad way. Just as the shock result of the British referendum on membership of the European Union pushed the pound down to thirty-year lows against other currencies, now the election of President Trump is seeing a huge sell-off of dollar assets against almost everything else. Only the Mexican peso is looking even weaker than the dollar, for obvious reasons. A minor crash in financial markets is already under way. Welcome to the Trump Slump. Problem is that the dollar isn’t just the American currency, it’s the world currency. Financial regulators all over the world require banks to hold government bonds in reserve, and the biggest stock of such stocks in the world are issued by the United States Treasury. The same goes for pensions regulators. The same goes for insurers. The same goes for the instincts of savers and investors everywhere. If a Trump presidency destabilises the dollar then it will destabilise, by definition, the entire global economy. Hence the sell-off in shares that is already happening. With the Nikkei down about 6 per cent, the Hang Seng down 3 per cent and the London market looking to start about 4 per cent down. By contrast gold, that safest of safe havens, is up to $1,300 again. One of the few brighter spots is that oil is a little weaker, though that is more a verdict on the suddenly more dismal prospects for global growth and the demand for commodities than some guarded relief that Hillary Clinton won’t be around to confront President Putin. Businesses, and markets, as we learnt post-Brexit, hate uncertainty, and what The Donald will do is, as yet, extremely uncertain. Obviously we do not know exactly what President Trump will do to the economy, but there have been some unsettling signs. He is unashamedly protectionist, and will tear up existing free trade agreements, such as Nafta, as well as abandoning other putative deals across the Pacific to East Asia and across the Atlantic with the European Union. There is some scant hope for the British that a Trump administration would be well-disposed to an arrangement with the UK, but the chances are that it wouldn’t be as generous towards Britain as Theresa May and her colleagues might wish. Donald Trump seems sentimental about Britain, but that won’t be enough. If there are American jobs at stake, then International Trade Secretary Liam Fox and British ministers can forget it. If improving international trade boost global growth, then the opposite is also true, and is very bad news for the world in the longer run. He may or may not make America great again, but he will not do much for the world’s prosperity. The man who prides himself on his ability to do a deal has previously indicated that he wants to start buying back US government debt at some kind of discount, which is not reassuring for those investors and financial institutions around the world that hold such paper.