content: To add to that, how often have we heard after these attacks that these people were 'known to police' or 'known to intelligence agencies'. They keep claiming that they could have caught these people 'if only we could have spied on them a bit more'. The police and intelligence services have a level of information gathering that is unprecedented in the history of the entire world. Never before have they been able to collect information on 99% of your life, and they're screaching and blaming that 1% they can't get access to as the reason they continuously drop the ball.  What I think is the opposite. I think they have so much information they can't even act on it. There are probably hundreds of thousands, maybe millions, of people in the UK who do suspicious stuff, who are involved in extremism in some form or another even if it's only twitter posting. They have so many people 'on watch' that there is no way they could positively identify a likely attacker unless that person were being incredibly overt about it.