The BBC's Newsnight is claiming a world first after interviewing an Al Qaeda double-agent.
A special report on the activities of the terror network is due to be broadcast on 15 November.
Editor Peter Barron told Press Gazette: "As far as I'm aware, this is the first time any journalist has had access to someone who has operated within Al Qaeda as a spy.
"The revelations are extraordinary. They show how Al Qaeda's terror network developed in Europe and Afghanistan, and how the intelligence services failed to respond to the threat. "The film puts the recent terror plots and trials into a chilling perspective."
The programme has uncovered the story of a man who, for seven years, moved around Al Qaeda's terror networks, while at the same time working as a spy for European intelligence services.
According to the BBC: "In a one-off Newsnight special, Omar Nasiri (not his real name) paints a unique portrait of the emergence of the terrorist threat — from his time in an Algerian terrorist cell in Europe to the training camps of Afghanistan, and from his meetings with top Al Qaeda officials, to his time spying on the mosques and militants who had made their home in London."
"Nasiri" will present a dramatic perspective on what the authorities knew about this threat and how far they understood it. The British intelligence services have been criticised in the past for their initial approach to radical Islamists. Prior to 2001, and even afterwards, the preaching of Islamic extremism at centres such as the Finsbury and Whitechapel mosques was permitted. It has been claimed such centres were considered by British intelligence to be "beacons of attraction", which they permitted to exist and then monitored.
Newsnight's story will provide new insights into Al Qaeda's work on biological and chemical weapons, as well as into how one key figure may have misled the US and UK into war in Iraq.
The special programme will also feature interviews with senior security and intelligence officials who worked in counter terrorism during the 1990s.