President Trump’s talk of taking Greenland isn’t a joke, that much is now clear. His ambition to "conquer" the autonomous Danish territory is a direct challenge to the EU, Nato, and the post-Cold War security order - so what should Europe do? Roland chats to Rachel Ellehuus, head of British defence and security think tank RUSI and formerly a senior US official in Nato and the Pentagon. She explains why Greenland matters far more than most people realise: from missile defence and Arctic