"can and must do more,"
Exactly. But unlike blaming Google and social media, how about realising that the nutjob was, once again, "known" to the spooks and had already been linked to extremism?
How about, oh I dunno, instead of signing off on every idea to pillage citizen's privacy, the PM and HomeSec understand that the security agencies are clearly incapable of doing their job with their current level of staffing. Sort that out first.