#Isis video purportedly shows murder of British hostage Alan Henning

Islamic State militants have published a video that is said to depict the murder of a British aid convoy volunteer Alan Henning three weeks after warning that he would be the next to die.

If the video is found to be authentic, Henning will be the fourth western hostage to have been killed by the group, following the video-taped beheadings of US journalists James Foley and Steven Sotloff, and Scottish aid worker David Haines.

The latest crime comes after the UK launched air strikes against Isis, joining the US and its Arab allies – Jordan, Saudi Arabia and the UAE – which had been targeting the group for several days.

Shortly before the Ministry of Defence announced that the RAF had attacked two Isis targets, the foreign office arranged for Henning’s wife Barbara to make a televised appeal for his release. His death, if confirmed, will be a devastating blow to her and to their two teenage children.

Intelligence agencies on both side of the Atlantic are studying the video in an attempt to verify its authenticity.

Henning, 47, a taxi driver from Eccles, Greater Manchester, had been held captive in Syria for nine months, and is thought to have been held by Isis with up to 20 other western hostages for much of that time.

Described by friends as “a big man with a big heart”, Henning fell into the group’s hands after joining a group of Muslim friends on an aid convoy to Syria last Christmas.

It was the second time in nine months that Henning had joined an aid convoy to Syria, after helping to raise funds to purchase the ambulances and medical equipment that were being taken into the country.

Other volunteers on the convoy have since described how he was separated from them after armed men surrounded a warehouse, a short drive from the Turkish border, where they were delivering ambulances and medical equipment. The gunmen were claimed that they were suspicious about Henning because he was not a Muslim, and because he had a chip in his UK passport. He was taken away despite the other volunteers demonstrating that all UK passports carried such a chip.

Henning was shown and named in a previous video posted online by Isis, which depicted the murder of Haines, 44, a father of two daughters from Perth in central Scotland.

At the end of the video, entitled A Message to the Allies of America, Haines’ killer was seen holding Henning by the collar of the orange jumpsuit in which he was dressed, and saying in a distinctive London accent: “If you, Cameron, persist in fighting the Islamic State, then you, like your master Obama, will have the blood of your people on your hands.”

Since the video appeared online, several leading Muslims had called for Henning to be released. One of them, Judge Sheikh Haitham Al Haddad, said that Henning’s murder would be “impermissible” under Islamic law.

Henning’s wife, Barbara, asked the Islamic State militants to “see it in their hearts” to release her husband, who she described as a “peaceful, selfless man”. She added: “Surely those who wish to be seen as a state will act in a statesman-like way by showing mercy and providing clemency.”

One of the organisers of the convoy, Kasim Jameel, a taxi driver from Bolton in Greater Manchester, described him as “a man who is full of compassion ... just a normal bloke, an everyday taxi driver who wanted to do good”.

The release of the video showing Haines’ murder and the threat to Henning’s life was followed by three more videos in which John Cantlie, a British photographer who has been held hostage by Isis for 22 months, delivered propaganda messages on behalf of the group.

Isis has also released an hour-long film about its advance across Syria and Iraq. In its final scene, a masked man with an US-sounding accent delivers a speech standing by Syrian soldiers who have been forced to dig their own shallow graves. It closes with the murders of the men.