The British hostage whom Islamic State militants have threatened to murder if US air strikes continue is an aid worker with 16 years' experience on humanitarian missions in some of the world's most volatile regions.
David Haines is thought to have been captured along with an Italian aid worker near a refugee camp at Atmeh in northern Syria almost a year ago.
He was shown in the militant group's last video, being restrained by the same masked British jihadist who had earlier been filmed murdering the American journalist Steven Sotloff.
Kneeling, his arms apparently bound behind his back and dressed in an orange jumpsuit, identical to that which Sotloff was wearing when he was killed, his full name – David Cawthorne Haines – appeared in a caption on the video, in both Arabic and English.
Haines remained silent. However, his captor appeared to threaten that the Briton would be killed if the UK joined the military action, saying, in his distinctive London accent: "We take this opportunity to warn those governments who have entered this evil alliance with America against the Islamic State to back off, and leave our people alone."
Shortly after the film was released the British government asked the media to withhold Haines's identity, at the request of his family, but within minutes his name was being published widely online by international news organisations such as the New York Times, the Washington Post and the Sydney Morning Herald.
Haines, 44, was born in east Yorkshire and grew up in Perth in central Scotland, where he attended Perth academy. He is understood to have been married twice, and has two daughters. For a number of years, he and his second wife, Dragana, who is Croatian, have been living near Zagreb, where they have operated a supplies business.
Haines spent several years working with a German NGO that was resettling refugees who had been uprooted by the civil war in the former Yugoslavia. He has also worked with NGOs in Libya and South Sudan.
Tiffany Easthom of the Belgian-based NGO Nonviolent Peaceforce, who worked with Haines for six months in 2012 in South Sudan, told NBC News he was "very familiar with insecure locations", adding: "He was very caring, had a good sense of humour."
Easthom said she understood that Haines had gone to Syria with a French NGO called ACTED. An Italian aid worker with ACTED who was captured near Atmeh at the same time as Haines was freed last May. Federico Motka, 31, later said he had been tortured and moved six times.
Six hostages have been released in recent months, in some cases after ransoms were allegedly paid to the kidnappers.
After telling MPs that the UK would not pay ransoms to secure the release of hostages in the hands of Islamic State militants, the prime minister, David Cameron, said Britain and the US would step up attempts to persuade other governments to cease making such payments.
The US state department says a small number of Americans are also being held by Islamic State. One is a 26-year-old woman who was also kidnapped while carrying out humanitarian aid work.
