But MI5 has been criticised after it emerged that the plotters met with two of the men who would later kill 52 people in Britain's worst terrorist atrocity.
Siddique Khan, one of the four men who blew themselves up in the capital on July 7th 2005, met with some of the fertiliser bomb plotters five times during a period of MI5 surveillance between 2003 and 2004.
On three of those occasions he was accompanied by fellow 7/7 bomber Shehzad Tanweer.
Jonathan Evans, director general of the Security Service, today admitted there were a "number of connections" between the two bomb plots, one of which was carried out to deadly and tragic effect.
But he insisted that MI5 "will never have the capacity to investigate everyone who appears on the periphery of every operation".
Responding to the question of why the July 7th London bombings were not prevented, Mr Evans concedes it is "deeply frustrating" the Security Service could not stop the "appalling" attacks.
Khan and Tanweer were not involved in the fertiliser bomb plot, the MI5 chief claims, instead appearing as "petty fraudsters" from surveillance footage; discussing fraudulent ways of raising funds with the five men convicted today.
But despite MI5's claims that the London bombers constituted only 0.1 per cent of Operation Crevice – the probe into the fertiliser bomb plot – a BBC1 documentary broadcast tonight questioned the Security Service's assertion that it did everything possible to prevent the July 7th bombings.
Tonight's Panorama asks why security operatives did not pass on information on Khan and Tanweer to West Yorkshire police after the former was tracked to his home in Dewsbury.
David Davis, shadow home secretary, and Menzies Campbell, leader of the Liberal Democrats, have both called for a full independent inquiry into MI5's July 7th terror attacks investigation.
When asked what MI5 should have said to West Yorkshire police Mr Davis told Panorama: "Broadly speaking, we have some suspects who are associated with, we think, some sort of terrorist, or potential terrorist, plot, can you tell us who they are, whether they've got form, what their background is, well, can you tell us their names for a start? And here's a photograph, and here are the addresses."
Fertiliser bomb plot ringleader Omar Khyam, 25, of Crawley, West Sussex; Waheed Mahmood, 34, and Jawad Akbar, 23, also of Crawley; Salahuddin Amin, 31, of Luton, Bedfordshire; and Anthony Garcia, 24, of Barkingside, east London, were all sentenced to life at the Old Bailey this afternoon.
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