British and American intelligence services are hunting for the Islamic State jihadist who beheaded an American journalist, and have identified him as a British Muslim extremist known as "John", according the Telegraph.
"John" is said to be the leader of a contingent of British fighters for IS nicknamed "The Beatles", due to their British nationality, and is described as "well-educated, intelligent, but highly committed member of the extremist terror group."
It comes amid revelations that British Muslims make up a quarter of the Islamic State's contingent of European fighters, accounting for around 500 out of the 2,000 European citizens currently fighting among its ranks.
While dozens of other European and western nationals are also fighting for IS (formerly known as ISIS), the disproportionate number of UK citizens traveling to fight under the black banner of jihad is once again drawing questions over how radical Islam has been allowed to fester unchecked in Britain for decades.
Foreign intelligence agencies have reportedly been frustrated by MI5 and MI6's ineffectiveness in dealing with home-grown Islamist radical. In June, the CIA sent a special contingent of agents to investigate the extent of Islamic extremism in the UK, in a snub to British intelligence agencies.
Last year, it was revealed that French intelligence had targeted London-based Islamic cleric and Al Qaeda-linked terrorist Abu Hamza for a potential assassination, out of frustration with growing British indifference to Islamist terrorism. Abu Hamza was eventually extradited to the US and jailed this year for serious terrorist offenses.
Britons have carried out numerous atrocities for the group, including suicide bombings. Most recently, the executioner of America journalist James Foley spoke with a clear London or south England accent.
Alarmingly, it is not the first time a British-born jihadi has been involved in a gruesome beheading: US journalist Daniel Pearl was decapitated by in Pakistan by British-born Islamist Ahmed Omar Saeed Sheikh in 2002.
Professor Anthony Glees, of the Centre for Security and Intelligence Studies at the University of Buckingham, told Britain's The Independent that political correctness had helped provide a fertile breading ground for Islamism in the UK.
"Why are there Brits there? In my view this is because Islamist extremist ideologies have been able to be spread with relative ease in our country under the cover of 'religion', 'free speech' and 'multiculturalism'."
"A small number of British Muslims have been brainwashed by so-called preachers... and convinced that they must kill to create a global caliphate," he added.
Muslim extremists wishing to volunteer for the Islamic State have found an easy passage to Syria by flying to Istanbul in Turkey, and from there crossing the porous southern border, according to Charlie Cooper, a researcher at the Quilliam Foundation, which monitors and combats Muslim extremism.
Cooper noted that the British man who beheaded Foley "will have committed himself entirely to furthering the aims of the Islamic state" and "completely rejected his British nationality".
ISIS fighters regularly stage public burnings of their passports in a rejection of all things non-Muslim, and the new "Islamic State" or "Caliphate" has even reportedly issued its own passports.
Shiraz Maher, a a senior researcher at the International Center for the Study of Radicalization at King's College London, said the fact that a British Islamist was chosen to behead Foley proves that UK nationals make up "some of the most vicious and vociferous fighters" in Syria and Iraq,
British Muslims are "very much at the forefront of this conflict," said Maher, who has been closely monitoring the evolution of Syrian jihadi groups.
"Unfortunately the British participation in the conflicts now raging in both Syria and Iraq has been has been one of full participation, one that has seen them at the front lines, taking part in the conflict in every way," he told The Daily Mail.
"So we have seen British fighters out there operating as suicide bombers, we have seen them operating as executioners. "Unfortunately they are amongst some of the most vicious and vociferous fighters who are out there. That is unfortunately just a part of their radicalisation."