Workers at a rare earth metals mine in Jiangxi province, China: the fact that China has put in place a ban on the export of such vital materials should signal to the entire global economy that it has muscles to flex. Photograph: Jie Zhao/Corbis via Getty Images You can bet your bottom dollar (if you’re still in that currency) that the various intelligence agencies will be concentrating their resources on ascertaining the negotiation agendas in the upcoming talks on Donald Trump’s tariff war. The European Union is – when it comes to the security of its negotiation process – at…