Email exchanges with a journalist claim a British man identified as the Islamic State executioner known as Jihadi John feared he was a dead man walking after run-ins with security services before fleeing to Syria to begin his reign of terror.

Computer programming graduate Mohammed Emwazi said he considered suicide after coming face to face with what he suspected to be a British spook as he attempted to sell a laptop computer in 2010.

In an email exchange with the Mail on Sunday at the time, Emwazi described how he became suspicious of the mystery buyer after they met.

It was also claimed Emwazi was part of a cell orchestrated by Osama Bin Laden to wreak terror on the streets of London, including in the failed July 21 bomb attacks in 2005.

It comes as British security services face pressure over accusations of failing to keep track of potential terror suspects and forcing desperate British Muslims into the clutches of Islamic extremist groups.