In the video that show’s American journalist James Foley’s beheading, the Islamic State militant that carries out his execution stands beside him, covered in black from head to toe.

James Foley Executioner Has British Accent

The identity of the militant is unknown, as he dressed to avoid recognition. The terrorist wears loose black pants, a black tunic and a black mask. The only areas not covered are his eyes and his hands that perform the brutal slaying. The best identifying marker made available through the video is the militant’s voice, which bears an British accent.

Prime Minister David Cameron, who is facing a large security threat in Britain, believes that the jihadi is indeed British. Linguists have narrowed it down further, deciding that he is likely from London. From his voice, it’s been determined that he is in his 20s and was either raised and/or educated in London and is speaking a “multicultural London English.”

"The person is taking great care to do 'posh talk,' as it were," University of London’s Institute of Education linguist John O’Regan told CBC. "They're very mindful of their p's and q's."

Who Is John The Jailer?

Didier Francois, a French journalist and former ISIL hostage, believes he might know who the masked jihadist is who beheaded Foley. “Recognized is a very big word, but I see roughly who it is,” Francois, who is a reporter with radio station Europe 1 said, according to the Daily Mail. Fellow French journalist and former hostage Nicolas Henin believes that the militant is “John the Jailer,” a jihadi that led a group of British Islamic State militants that called themselves “The Beatles.”

It is thought that since “John” lived for a considerable about of time in the U.K. that he will have met and known a number of people who could help investigators identify him. Richard Barrett, a former head of counterterrorism for Britain's MI6 intelligence agency, said, "He will have had many acquaintances and friends in the United Kingdom and those people will wish to see him brought to justice."

Britain's Metropolitan Police and British intelligence agencies are currently in search of the militant.