British prime minister David Cameron yesterday abandoned his family holiday to return to Downing Street for talks with foreign secretary Philip Hammond and intelligence and military officers.
The apparent involvement of a British citizen follows his recent warnings that the UK must help to defeat Islamic State because of the security threat it poses to the UK.
US authorities yesterday confirmed the authenticity of the video, which shows Mr Foley in an orange jumpsuit, kneeling before his throat is cut. His severed head is shown dumped on his body before the killer warns another kidnapped journalist, Steven Sotloff, will be executed next.
The militant who appeared in video, who called himself John and is believed to be from London, was identified by one of his former hostages as the ringleader of three British jihadists thought to be the main guards of foreign nationals in Raqqa, a stronghold of Islamic State rebels