The masked ISIS militant known as "Jihadi John" who was seen in several Islamic State videos of the beheading of British and American hostages has been identified. His name is Mohammed Emwazi and he is a 26-year old West Londoner, born in Kuwait. He graduated in 2009 in information technology and is fluent in Arabic.

Emwazi's first appearance as an ISIS militant was last August when he appeared in a video apparently killing American journalist James Foley. He would later appear in the videos of the beheadings of British aid worker David Haines, taxi driver Alan Henning, US journalist Steven Sotloff and American aid worker Abdul-Rahman Kassig.

Most recently he featured in the video where Japanese hostage Kenji Goto was beheaded. He is one of the three British jihadists, known as "the Beatles", assigned to guard hostages abducted by ISIS in Syria.

The British security services knew his identity and had dealt with Mohammed Emwazi before. In 2010, Emwazi filed a complaint with the Independent Police Complaints Commission claiming to have been harassed and threatened by the British security services.

His complaint came after a trip to Tanzania, in August 2009, where he was detained by the authorities and flown to the Netherlands where he was to be interrogated by the MI5. The security services believed he was heading to Somalia to join the militant group al-Shabaab.

He was arrested and interrogated again before leaving Britain and moving to Kuwait. In 2010, he visited London to finalize plans to marry a woman in Kuwait and was arrested by counter-Terrorism officials in the UK. In his complaint he claims to have been "strangled" during these interrogations. He was never allowed to fly back to Kuwait by the authorities.

His friends say he was desperate to leave the UK and in 2012 he evaded the authorities and reached Syria to join the Islamic State militants.

David Cameron's spokesman says they won't confirm or deny "anything related to intelligence" for obvious operational reasons but US government officials have already confirmed Emwazi's identity to reporters.