You could insert Brexit, but that would be a bit narrow minded. There is a wide choice to choose from including Trump, Iran, Boris, Italy, China, EU, tariffs, border delays, as well as Brexit. What they all have in common is an impact or potential impact on trading and your business if you use something that originates over the water. No one knows how Brexit will work out is practice - the only guarantee is there will be a lot of hot air generated about it. But with plenty of potential for disruption from elsewhere you should look at strengthening you supply chain anyway, if you have not already done it.