HOW WAS ABEDI ALLOWED TO SLIp UNDER THE RADAR?

HOME Secretary Amber Rudd was facing questions last night over how the Manchester Arena bomber snuck under the security radar despite a series of warnings.

Suicide bomber Salman Abedi was able to return to the UK from Libya and detonate his deadly device despite at least five warnings going unheeded.

However, the security services hit back last night saying that they have had 500 investigations and foiled 18 plots since 2013 – including five since Islamic extremist Khalid Masood went on the rampage in Westminster on March 22.

However, Ms Rudd has admitted attacker Abedi, 22, was known to the security services “up to a point”. Reports have suggested that people who knew Abedi had raised the alarm over his extremist views in the years before the atrocity.

One former senior security figure said: “Knowing of someone’s radical sympathies and knowing they present a real and present danger are very different things. So the essence of the security dilemma is how to assess who and when to investigate very deeply, given the resources needed for 24/7 surveillance.

“For every suspect that appears to be high priority another has to be pushed down the list. So who not to investigate urgently is as important a decision as who might be worth investigating.”

Security chiefs have repeatedly made clear that all extremists cannot be kept under close watch all the time.