David Cameron is expected to announce air strikes as early as next week against the Islamist “monsters” who murdered David Haines and are threatening the life of another British hostage.
Mr Haines became the first Briton to be murdered by a man believed to be the British-accented terrorist known as “Jihadi John”, who has previously beheaded two American journalists.
In the footage, released on Saturday night, the terrorists threaten to murder a second British captive – Alan Henning, a 47-year-old aid convoy volunteer from Manchester who was captured in Syria late last year.