MI5 and MI6 have identified the British fighter suspected of murdering the American journalist James Foley, senior government sources confirmed last night.

The masked man with a London accent, who is said to be known to fellow fighters as “Jihadi John”, was seen in the shocking video of Foley’s death released by the Isis extremist army last week.

While sources gave no details of the man they have identified, a key suspect is Abdel-Majed Abdel Bary, 23, who left his family’s £1m home in Maida Vale, west London, last year. He recently tweeted a picture of himself holding up a severed head.

Writing in The Sunday Times today Philip Hammond, the foreign secretary, says Isis is “turning a swathe of Iraq and Syria into a