Mark White from Sky News reported:
More than 400 former jihadi fighters back in Britain, say security sources
Returning extremists could be back in the UK awaiting instructions on when to attack, a security expert tells Sky News.
UK authorities are facing an increased terror threat from battle-hardened fighters returning from Mosul and other conflict zones in Iraq and Syria.
Security sources have told Sky News more than 400 former fighters are now believed to be back in Britain.
The authorities believe there is a growing risk the UK could suffer the kind of mass gun and bomb attacks seen in France and Belgium recently, as many returning fighters will have been trained in the use of weapons and the construction of improvised explosive devices.
It is a serious, two-pronged challenge for the police and security services, who are already working flat-out to counter the threat from homegrown lone-wolf extremists, like Khalid Masood, who launched last week’s deadly attack on Westminster.