A former hostage of the Islamic State (IS) has identified the executioner of American journalist James Foley, whose beheading was filmed and posted on social media by the terrorist organization on Tuesday.

According to the Guardian, the former hostage was guarded by the executioner, identified as a Londoner named John, in Raqqa, an Islamic State stronghold in northern Syria. "John" is purported to have been the primary negotiator in talks to release 11 hostages earlier this year, resulting in their handover to Turkish officials.

Meanwhile, the Telegraph described the militant as intelligent and "highly committed" to the IS cause, and, along with another two British nationals, is believed to be in charge of guarding the Islamist group's foreign hostages. Owing to their common nationality, the three are referred to by the hostages as "The Beatles."