Johnson: We Must Crack Down On UK Jihadists

London Mayor Boris Johnson has said Britons who travel to fight in Iraq and Syria without telling the authorities should be presumed to be potential terrorists until they are proven innocent.

His is the latest voice to call on the Government to take tougher measures to combat extremism, following the murder of US journalist James Foley by an Islamic State (IS) militant, dubbed 'Jihadi John', who is believed to be British.

Mr Johnson, who has overall responsibility for the Metropolitan Police, warned that to do nothing and allow IS, formerly known as ISIS and ISIL, to establish a "caliphate" would mean a "tide of terror will eventually lap at our own front door".

"We are going to have to make up our minds very quickly about this 'caliphate': how we will respond to the irruption of a new and hellish country on the map, and how we deal with these Brits who go off and fight in its name," he said, writing in his Daily Telegraph column.

"The place would be a giant training ground for terrorists and wannabe jihadis. We need to try to close it down now, before it gets worse."

He said the IS "wackos" must be tackled and joined growing calls, including from former shadow home secretary David Davis, for Britons fighting abroad to be stripped of their citizenship, and said control orders should be brought back immediately for the most serious cases.

"We need to make it crystal clear that you will be arrested if you go out to Syria or Iraq without a good reason," he said.

"The law needs a swift and minor change so that there is a 'rebuttable presumption' that all those visiting war areas without notifying the authorities have done so for a terrorist purpose."

And he suggested the reportedly English jihadist who beheaded Foley, whom British intelligence agencies are close to identifying, should be killed in a bomb attack.

Mr Johnson said: "Young men such as this killer are famously told that if they die in 'battle' they will be welcomed in heaven by the sexual ministrations of 72 virgins.

"Many of them believe it - even though scholars have suggested that the reference to 'black-eyed virgins' is in fact a promise of 72 raisins. I suspect most of us don't give a monkey's what happens to this prat in heaven, whether he meets virgins or raisins - we just want someone to come along with a bunker-buster and effect an introduction as fast as possible."

Foreign Secretary Philip Hammond has also warned that IS fighters will " seek to strike us on British soil " if they are not stopped.

Writing in the Sunday Times, Philip Hammond said it was horrifying that the perpetrator "could have been brought up in Britain" and said the Government was investing "significant resources" to tackle "a barbaric ideology".

The UK Government has also appointed Lieutenant General Sir Simon Mayall as security envoy to the Kurdistan region of Iraq to help with efforts to defeat IS.