In reality these stupid Muslim terrorists can attack just about anybody they please, in an open society like Britain. They can pop up whenever and wherever they like, jump up and down, jabbering at high speed and then proceed to murder whoever takes their fancy. The don't appear to understand logic or rational, so I'm nor sure how we are supposed to stop them. Britain isn't a police state, and is governed by consent, not by force. Good intelligence would seem to be the only answer. There have been a few high-profile cases recently where terrorist cells have been intercepted before they strike, but sadly not in this case it would seem. But apart from arresting everybody in Britain who isn't white, Anglo-Saxon and Christian, and dumping them at Calais, I can't see what else there is to be done.