Terror threat

There's a reason why so many terrorists like Salman Abedi have had dealings with British intelligence before

The full extent of the security services' knowledge of Manchester bomber Salman Abedi may never be known. But it seems clear that MI5 and counterterrorism police were first made aware of his extremist thinking five years ago when classmates warned of his support for suicide attacks.

Politicians have rightly begun to ask why a known Islamist extremist, if not a terror suspect, wasn't stopped before he carried his bomb into the Manchester Arena on Monday night.

When MI5 comes to review its intelligence on Abedi, their officers will have to recognise they have been here before.

Before all the major terror attacks committed in the UK since, and including, the 7/7 London bombings, the security services had knowledge of, or even dealings with, at least one of the suspects.