An Islamic State militant speaking with an English accent, has threatened Britain in an internet video showing the killing of five "spies" it said worked with the international coalition fighting IS in Iraq and Syria.
The SITE Intelligence Group said the video shows five men from Raqqa, capital of the self-declared jihadist ‘caliphate’ straddling Syria and Iraq, confessing to carrying out acts of espionage.
In it, the English IS fighter mocks British Prime Minister David Cameron for challenging IS, and calls him an "imbecile".
He said those who want to continue fighting "under the banner of Cameron" should ask themselves: "Do you really think your government will care about you when you come into our hands, or will they abandon you as they have abandoned these spies and those who came before them?"
The five men are then killed with a bullet to the head.
The latest video thought to have been sent by Islamic State is aimed at "threatening, goading and provoking" its opponents in the West, a security expert claims.
The sight of a masked executioner declaring in a British accent that David Cameron is an "insignificant leader" who dares to "challenge the might of the Islamic State" has been timed to strike terror internationally while the extremists have suffered several tactical setbacks on home ground, according to Shashank Joshi a senior research fellow at the Royal United Services Institute (RUSI).
In what is a "more slickly-created propaganda video than their rivals can manage" IS are hoping to "compensate for their recent string of failures" not just in the key Iraqi city of Ramadi in recent weeks to state forces, but also in Sinjar and their weakening power in places like Raqqa in Syria.
Mr Joshi said of the timing of the unverified video: "I think there is an overall sense in which they have had relatively few successes in the past few weeks.
"They have been pushed back and these videos are a method to try and maintain support."
Through the video IS is targeting both their own supporters and their opponents at the same time.
They hope to bolster support from their backers while also intimidating members of the public from the range of nations who have opposed IS including Britain, Australia and the US, according to Mr Joshi.
He said: "The videos are effectively propaganda to raise the level of threat .
"It is about striking terror into our minds - they are threatening, goading and provoking us.
"The stronger their (IS's) reputation, the more people who will travel to their caliphate, the more recruits they can have around the world and the more people will travel to Syria and Iraq and so they can potentially eclipse their rivals. "
Reports have also suggested that a child appears in the video.
This would be another cynical move by IS because "they use their messengers very carefully," according to Mr Joshi.
He said: "It is more manipulation of us and therefore more threatening.
"The child would be a reminder of the danger of IS and also of how they see themselves as a nation building process. They have indoctrinated families and children under their control and also indoctrinated children to do brutal things.
"It is a reminder of how they use children as a threat and to further their propaganda."
Mr Joshi suggested that people should be looking at these videos with "a jaundiced eye" and they should be viewed "sceptically and as propaganda".
The masked man is the latest purported IS figure appearing to have British roots.
"Jihadi John", the British extremist Mohammed Emwazi, appeared in videos showing the execution of Britons David Haines and Alan Henning, plus those of US journalists James Foley and Steven Sotloff. Emwazi was killed in a US drone strike in Syria in November.
Whitehall sources suggested the video was an attempt to distract attention from recent military setbacks IS has faced, like losing the Iraqi town of Ramadi to state forces.
In the latest video the man goes on to say that IS will invade the UK and rule under Sharia Law.
He adds: "As for those of you who wish to continue fighting under the banner of Cameron, on the minimum wage, we say to you, to ask yourself, do you really think your government will care about you when you come into our hands? Or will they abandon you, as they have abandoned these five and those who came before them? Because you will lose this war, as you lost in Iraq and Afghanistan."
It comes days after Mr Cameron promised to crack down on IS sympathisers, stressing in a New Year's message that all Britons should have "loyalty" to their country.
The Prime Minister said 2016 would be a "test of our mettle" as he pledged action to tackle the "poisonous narrative" which led some Britons to turn against their country.
He said the UK should "revel" in its way of life rather than "appease" extremists, and all who live in the country must sign up to its values.
A Foreign Office spokesman said: "We are aware of the video and are examining its content."
