Jihadi John who has now been identified as Mohammed Emwazi from West London, became known to British intelligence agencies back in 2009.
He was known to officials and had been detained by security services in the past.
British campaign group Cage claim Emwazi was interrogated by MI5 before its agents tried to recruit him as an informant.
The Mail Online report: British security forces were facing difficult questions yesterday as it emerged that ISIS killer Mohammed Emwazi, known as Jihadi John, was brought to their attention five years ago.
He was deemed to be so significant within terror circles that MI5 allegedly tried and failed to recruit him, and yet he was able to slip the net and begin his reign of terror in the Middle East.
Born in Kuwait, he moved to London with his family aged six and later graduated in computer programming at the University of Westminster.
As long ago as 2007, Emwazi was involved in a West London offshoot of the Al Qaeda-inspired Al Shabab terror group in East Africa.
Two members of that group were later to die in US drone strikes in Somalia, another vanished in a black cab despite being on a government control order and Emwazi was himself detained at the request of the British after travelling to East Africa.
He claimed he was then questioned and harassed by MI5, who are said at one time to have tried to ‘turn him’ in to becoming a source.
In fact, Emwazi may have come into contact with security sources as many as a dozen times over the years, The Telegraph reports.