Here we go again. Another terrorist attack in Europe seemingly connected to the outrages last year in Paris featuring a Brussels centred cell of Isis this time in Brussels itself taking 34 lives so far and injuring hundreds involving bombing the Airport as pictured above and the Metro.
Investigations no doubt will continue into how it was two people were able to bring the explosives into the departure lounge and what if anything Belgium know about the high level terrorism alert that started Friday with the arrest of a suspect from the Paris attacks.
One thing is though is just how we can balance the concept of 'open borders' not least the common border scheme in Europe that the UK isn't a part of and at the same time deal effectively with people who attempt to use it to cause mayhem and murder on our streets.
A chain is only as strong as it's weakest link and there are some indications some countries are less effective at applying checks that a person having gotten through are able to move with ease elsewhere.
Equally while I'm sure nearly all migrants arriving have no truck with terrorism, can we be sure others are not taking advantage of this to get in?