Britain faces a "new wave" of home-grown terrorist attacks led by up to 800 Muslim ex-prisoners who have been radicalised by jihadists while serving their sentences, a think-tank has warned.
Large-scale and co-ordinated attacks such as the 7 July bombings are likely to be replaced with terrorist assaults by highly motivated but poorly trained lone individuals whose lack of connection with any major terrorist organisation will make them more difficult for police or MI5 to detect.
A study published in the journal of the Royal United Services Institute (Rusi) warns that one of the key threats from this next generation of terrorists comes from within the ranks of the 8,000 Muslims currently serving prison terms who are at risk of being converted to extremism by hardcore inmates jailed for terrorist offences.
The report cites estimates by prison probation officers that up to one in 10 Muslim inmates are being successfully targeted while inside jail, leading to the creation of a new generation of potential attackers who are due for release in the next decade and whose previous convictions do not relate to terrorism.
All major sporting events such as this year's Commonwealth Games in India and 2012 Olympics in London should be considered as possible targets for this new generation of "lone killers" who have been radicalised by preachers in the hope that eventually at least one of their number will be successful.
Michael Clarke, director of Rusi and co-author of the study, said: "Perhaps some 800 potentially violent radicals, not previously guilty of terrorism charges, will be back in society over the coming five to ten years... The natural reaction to improved counter-terrorist operations is for jihadist attacks to evolve towards more individual efforts."
The report suggests that radicalisation is taking place in British prisons at a rapid rate, especially in the eight high-security establishments where most terrorism offenders are detained.
Abu Hamza, the former night-club bouncer who became a figurehead for radical Islam in Britain before being jailed for seven years for soliciting murder, is held in a special unit at Belmarsh Prison in south-east London partly to minimise the risk that he will indoctrinate other inmates.
The Rusi study said the evolution of the threat posed by Islamist groups away from highly organised attacks with a recognisable leader to unsupported individuals was already apparent in America, where the recent attempt by the Pakistani America Faisal Shahzad to carry out a car bombing in Times Square in New York showed a new reliance on untrained but radicalised attackers.
The Ministry of Justice said it did not agree that radicalisation was widespread within the prison system. A spokesman said: "We run a dedicated expert unit to tackle the risk posed by those offenders with violent extremist views and those who may attempt to improperly influence others."
Influential and behind bars
The former preacher at London's Finsbury Park mosque was jailed for terrorism offences in 2006 and remains on remand in the high-security unit of Belmarsh prison, where he is isolated from other prisoners.
The Jamaican-born preacher, born Trevor Forest, was jailed in 2003 for stirring up racial hatred. A number of convicted terrorists, including the shoe bomber Richard Reid and the 9/11 plotter Zacarias Moussaoui, attended his sermons. He was deported from Britain in 2007.
Ahmed Abdullah Ali
The leader of the 2006 plot to blow up airliners with liquid bombs is serving a 40-year sentence after being convicted of helping to recruit and train fellow jihadists, persuading them to record suicide videos and prepare for martyrdom.
Muktar Said Ibrahim
The "emir" of the failed attacks on the London transport network on 21 July 2005 attended the Finsbury Park mosque and was found with recordings of preaching by El-Faisal. Ibrahim helped to recruit his co-conspirators for the botched attack. He is serving a 40-year sentence.