Mikey, I’ve told you before. Most, if not all of the people who have committed these atrocities were known to the security services. Numbers are so great (not ‘a few’ as you claim) that it is impossible to monitor them all 24/7. Furthermore, ‘good intelligence’ will never, on its own, stop random attacks. These people need to be removed from our society permanently, and whilst that will never stop it altogether, it will stop known suspects from achieving their ambition and hence, make the world a little safer.