This is the gravest crisis for Western security since the end of World War Two, and a lasting one. As one expert puts it, "Trumpism will outlast his presidency". But which nations are equipped to step to the fore as the US stands back? ... Donald Trump is the first US President since World War Two to challenge the role that his country set for itself many decades ago. And he is doing this in such a way that, to many, the old world order appears to be over - and the new world order has yet to take shape....