British intelligence agencies MI5 and MI6 have identified the man suspected of the horrific beheading of American journalist James Foley, according to British media reports.
The hooded man with an English accent is believed to be 23-year-old Abdel-Majed Abdel Bary, known to fellow Islamic State militants as Jihadi John.
The former rapper left his family home in an affluent west London suburb last year to fight in the civil war in Syria, reports an article on The Sydney Morning Herald.
In early August he tweeted a photo of himself wearing military camouflage and a black hood, while holding a severed head in his left hand.
British SAS forces are hunting Foley's killer, using a range of high-tech equipment to track him down and potentially free other hostages
The Mail on Sunday is reporting that a "significant force" of SAS personnel has been deployed to northern Iraq over the past two days, joining local units fighting the Islamic State.
They have fanned out into four-man teams, accompanying Iraqi and Kurdish troops in an effort to find British jihadists.
The Sunday Times reports that Bary is the key focus of the manhunt. He is one of the British jihadists referred to by former hostages as the Beatles because of their British accents. The two others were called "George" and "Ringo".
The two other Britons suspected of involvement in the crime are Aine Davis, a former drug dealer who converted to Islam, and Razul Islam, who is believed to have joined the terrorist group that murdered Foley.
Bary is the son of an Egyptian-born militant who is awaiting trial on terrorism charges in Manhattan, due to his alleged involvement in the bombing of US embassies in Kenya and Tanzania in 1998.
Before leaving the family home to fight in Syria, Bary was an aspiring rapper known as L Jinny whose music was played on one of Britain's most popular radio stations, BBC Radio 1.
Recordings of his songs will prove vital to the investigating team, with experts using voice recognition technology to match his voice with that of the man who brutally decapitated Mr Foley.
Bary made a number of music videos for his songs, with titles such as Flying High, Dreamer and Overdose.
It is believed he was indoctrinated by an Islamic preacher named Anjem Choudary who persuaded him to join the fight in Syria.