The video then shows a man in an orange jumpsuit on his knees, believed to be British aid worker David Haines.

Behind him stands a sinister figure all in black, brandishing a knife.

Based on his appearance and voice, it is believed this the same executioner who killed James Foley and Steven Sotloff – the notorious Jihadi John.

11:31 pm

The new video again has again been made with high production value.

It begins with a news clip of David Cameron talking about Britain’s foreign policy towards ISIS.

The Prime Minister is explaining that Britain will be working “with allies” to combat the rise of this “appalling organisation”.

The clip cuts out as if a television is being turned off.

A message in Arabic is followed by one in English which reads ‘A message to the allies of America’.

11:22 pm

The Foreign Office has been contacted about tonight’s new video.

The FCO says it is “working urgently to verify” the video purporting to the show the execution of the British aid worker.