In an interview with the BBC, Foreign Secretary Philip Hammond acknowledged that the apparent executioner spoke with a British accent and said the video seemed to be genuine.
Hundreds of Britons are believed to have traveled to Syria to fight in the country’s civil war, including many who have joined the Islamic State.
“We’re absolutely aware that there are significant numbers of British nationals involved in terrible crimes, probably in the commission of atrocities,” Hammond said. “Many of these people may seek at some point to return to the U.K., and they would then pose a direct threat to our domestic security.”
A European intelligence official said the British government was examining the video, and the speech of the purported executioner, to compare it with former Guantanamo Bay prisoners and other British residents believed to have joined the Islamic State.
Both prisoners in the video are wearing orange shirts and pants, similar to orange jumpsuits worn by detainees at the U.S. military prison at Guantanamo Bay, Cuba. A similar outfit, believed to be a jihadist symbol of the prison, was worn by Nicholas Berg, an American businessman kidnapped in Iraq in 2004 whose execution by an Islamic State precursor organization was recorded on video and posted online.