So I read the police/security services have 3000 people on a watchlist and 500 "plots" under investigation. I'm normally very much for rule of law, and I don't think my idea honestly deviates much from that, but why can't they just arrest all of these people. It would take extraordinary measures and resources, but we're a county that can magic up hundreds of billions for quantitave easing or Trident, why not for the security of the citizens?
If there's 3000 people being watched, if they have evidence of ISIS sympathies and so on, that should be enough. That right there, given how quickly it feels like it takes these people to just decide to do an attack, and the fact that their state of mind does not care whether they die at the end, why can't we go and arrest and detain every single person who poses enough of a threat that they are currently under investigation?
And before anyone says, yes I ONLY want people who we have concrete evidence on, of showing sympathies with ISIS. Messages intercepted, talking on message forums about wishing harm on civilians, that should be enough. Once their minds are thinking like that it takes 5 minutes for them to grab a knife, at whatever moment they finally crack, and just create a terror incident like this. Enough is enough.