Jihadi John to be unmasked 'within days': Identity of masked British executioner to be revealed as FBI prepares to arrest 12 of his UK associates

Anti-terror police are set to arrest up to 12 British associates of Islamic State executioner Jihadi John, it has been reported. 

British and American authorities say they know the identity of the hostage killer - and are set to reveal it within days. 

The executioner is one of four British jihadis known as the 'Beatles' holding hostages in Syria. They said : 'We are 99.9% certain now as to who ‘John’ is but investigators have had to tread softly in charting and approaching his wider network in the UK.

'Familiar names of what can only be described as hardened extremists with a jihadi background have cropped up in this investigation.'