Briton, 26, named as man behind gruesome beheading videos, had been detained by security services in the past.
The British man who was named as the extremist glorying in the beheading of journalists and aid workers had been known to intelligence agencies for five years before he publicly emerged in a series of grisly Islamic State (Isis) propaganda videos.
It has been confirmed to the Guardian that Mohammad Emwazi, a 26-year-old Londoner and computer studies graduate, is the militant labelled “Jihadi John” who has claimed responsibility for the beheadings of at least seven US, British and other hostages.
Emails and other documents that emerged on Thursday also showed that security services had been tracking Emwazi since 2009, starting when he was refused entry to Tanzania, until the middle of 2013 when they informed his family that he had crossed over to Syria.
During that period Emwazi complained on occasion that he had been harassed by M15, but the Kuwaiti-born Briton eventually disappeared before arriving on the world stage as the murderous public face of Isis in August 2014.