Behind the mask: Jihadi John's beheading videos shocked the world
The man who became known as Jihadi John first appeared in a brutal video appearing to show a beheading that caused global shock.
Dressed in black with a balaclava covering all but his eyes and the ridge of his nose, and a holster under his left arm, he spoke with a British accent, going on political rant before apparently killing US journalist James Foley.
He reappeared in videos of the beheadings of US journalist Steven Sotloff, British aid workers David Haines and Alan Henning, and American aid worker Peter Kassig before featuring in a video with Japanese hostages Haruna Yukawa and Kenji Goto, shortly before they were killed.
It was six months after he first came to prominence when the jihadist was unmasked as Kuwaiti-born Mohammed Emwazi, who moved to the UK aged six.
Emwazi, who alongside three other IS captors had gained the nickname the Beatles, was described by one former hostage as a lead figure in the militant group.
Javier Espinosa, a Spanish journalist who was released after being held for six months, described being subjected to a mock execution and accused the man known as Jihadi John as wanting "maximum drama".
That image of a psychotic killer is at odds with the picture painted of a young Emwazi who grew up in London.
His former headteacher at Quintin Kynaston Community Academy in the north of the city recalled a "hard-working aspirational young man".
She said he had been bullied at school but insisted she was not aware of any radicalisation of pupils there.
He went on to gain a degree in information systems with business management from the University of Westminster.
Emwazi went on to work with an IT firm in Kuwait during a stint in the Gulf and was described by a former boss as "the best employee we ever had" and a "calm and decent" person.
Claims earlier this year by campaign group Cage that he was harassed by British security services, driving him to extremism, were branded "reprehensible" by Downing Street.
He was known to intelligence services in the UK since at least 2009 and had been on a list of potential terror suspects.
After Emwazi was identified as the man in the videos Cage director Asim Qureshi, who had been a former confidant, controversially described him as a ''beautiful young man''.
Last month Cage admitted it made mistakes in its handling of the issue, but added that they believed their intervention had made an "important contribution to the debates around security services' accountability".