If we have learnt one thing in the last decade it is that Donald Trump cannot be trusted... and any national leader who doesn't proceed on the basis of that one fact is a fool.
(Some of you might argue this is really not so novel, US Presidents have never been trustworthy, and that may be right, but the Tangerine Tyrant doesn't even seek to maintain the useful pantomime of international affairs; which has been destructive, but perhaps also useful?)