The British man named as ISIS executioner Jihadi John revealed his hatred and fear of security services in a series of emails in 2010, saying he considered suicide because he felt like a “dead man walking”.

Mohammed Emwazi was indeed being watched by MI5, which had been aware of his extremist links for six years before he apparently appeared on video beheading American journalist James Foley in August.

According to Cage, the ISIS executioner had told a journalist four years ago that he felt like a "dead man walking” due to the harassment and constant surveillance of British security services.

"Sometimes I feel like I'm a dead man walking, not fearing they may kill me. Rather, fearing that one day, I'll take as many pills as I can that I can sleep forever!! I just want to get away from these people!!!," the rights group quoted Emwazi as writing.

Prime Minister David Cameron, however, has strongly rejected the report, while Boris Johnson, the mayor of the British capital city of London, accused the rights group of justifying Emwazi’s acts of terror.