article: He is Mohammed Emwazi, a Kuwaiti-born British man in his mid-20s from west London, who was previously known to British security services. British police declined to comment, citing ongoing investigations. Emwazi first appeared in a video last August, when he apparently killed the US journalist James Foley. He was later thought to have been pictured in the videos of the beheadings of US journalist Steven Sotloff, British aid worker David Haines, British taxi driver Alan Henning, and American aid worker Abdul-Rahman Kassig, also known as Peter. In each of the videos, the militant appeared dressed in a black robe with a black balaclava covering all but his eyes and top of his nose. Speaking with a British accent, he taunted Western powers before holding his knife to the hostages' necks, appearing to start cutting before the film stopped. The victims' decapitated bodies were then shown. Earlier this month, the militant featured in a video in which the Japanese journalist Kenji Goto appeared to be beheaded. Hostages released by IS said he was one of three British jihadists guarding Westerners abducted by the group in Syria. They were known collectively as "the Beatles". Mohammed Emwazi timeline: Source: Cage, London-based campaign group 'Jihadi John' movement mapped Emwazi "claimed harassment" In a news conference, Asim Qureshi, the research director of the London-based lobby group Cage, which had been in contact with Emwazi over a number of years, explained how he had been approached by the Washington Post for the story and detailed the difficulties Emwazi had had with security services in the UK and overseas. Mr Qureshi said Emwazi, who is understood to be about 27, had been "extremely kind, gentle and soft-spoken, the most humble young person I knew". He said he could "not be 100% certain" Jihadi John was Emwazi although there were "striking similarities". Emwazi's difficulties began when he travelled to Tanzania in May 2009 following his graduation in computer programming at the University of Westminster, Mr Qureshi added. He and two friends had planned to go on a safari but once they landed in Dar es Salaam they were detained by police and held overnight. Emwazi then ended up flying to Amsterdam, in the Netherlands, where he claimed to be met by British intelligence agents from MI5 who accused him of trying to travel to Somalia, where the jihadist group al-Shabab operates. He denied the accusation and said the agents had tried to recruit him before allowing him to return to the UK. Analysis: Frank Gardner, BBC News US and British counter-terrorism officials discovered the identity of "Jihadi John" as far back as last September. The FBI, Britain's MI5 and other intelligence agencies used a combination of voice recognition software, interviews with former hostages and on-the-ground research in London to build up a profile of the man now revealed to be Mohammed Emwazi. They have always declined to reveal the name for "operational reasons". Now that it's out in the public domain, it's emerged that Emwazi was well-known to MI5 and that it even tried to recruit him as an informer,
summary: The masked Islamic State militant known as "Jihadi John", who has been pictured in the videos of the beheadings of Western hostages, has been named.