London: Mohammed Emwazi, the masked Islamic State (IS) killer who has appeared in several execution videos, was part of a terrorist cell that was behind the failed bomb attack in London on July 21, 2005, according to media reports.
One member of the terrorist network was in touch with Hussein Osman, who was later jailed for life for placing an explosive at London's Shepherd's Bush underground train station, the Observer reported.
The failed terrorist attacks on July 21, 2005 came a fortnight after four men blew themselves up on London Underground trains and a bus, killing 52 people and injuring more than 700, in what was the worst terrorist atrocity committed on British soil.
Emwazi, now infamous as "Jihadi John", was able to hoodwink the British security agencies and slip out of the country in 2013 using false documents and emerge in Syria a year later, though the agencies were aware of his links to the London bombers.
The revelations, contained in court documents seen by the Observer, raise urgent questions over how Emwazi was able to evade surveillance and escape, re-emerging as the world's most wanted terrorist.
Emwazi was a "person of interest" for the British intelligence service MI5, as a member of a London jihadi cell set up in 2007 to recruit for the al-Shabaab, an Al Qaeda affiliate.
British Shadow Home Secretary Yvette Cooper called for an urgent review into whether the government's decision to weaken counter-terrorism laws had played a role in Emwazi being given the chance to travel to Syria and become a figurehead for the IS.
MI5 had been aware of Emwazi for six years before he appeared on a hostage video for the first time in August 2014, but apparently was unable to control the network of which he was a part.
"We need to know whether Theresa May's (British Home Secretary) decision to ignore all our warnings and weaken counter-terror powers has made it easier to organise and recruit for ISIL (IS)," Cooper said.
"Suggestions of possible links between those carrying out atrocities on behalf of ISIL (IS), and those behind the 21/7 planned attack on London, are very concerning," she added.
"The problem with UK (British) counter-terrorism legislation over the past decade is that it has become a patchwork of knee-jerk responses to specific events, rather than something that has really been thought through," said Nigel Inkster, a former deputy chief of the British secret service MI6.
The widow of British aid worker David Haines, apparently killed by Emwazi has said that she wants him caught alive.
British Prime Minister David Cameron has defended the country's security services amid criticism they failed to stop Emwazi, from joining the IS in Syria.
On Friday, he vowed to hunt down the IS executioner and put him "out of action".