The controversial policy of detaining foreign terrorist suspects without trial was a key tool in preventing Britain from being attacked by al-Qa'eda militants, senior security officials believe. The officials say that the emergency measure, introduced after the September 11 attacks on America, deterred scores of terrorists from entering the United Kingdom, and they fear that ending the policy will increase the chances of an attack here. Charles Clarke, the Home Secretary, told the Commons last week that he was bowing to a law lords ruling to end the detention of foreign nationals suspected of threatening national security.In future terrorist suspects, including those with British nationality, would be subject to a wide range of "executive control" orders, including house arrest and electronic tagging. The officials said they would have to "wait and see" whether the powers would be as effective. One security official added, however, that the threat from terrorism was as "real today as it was in the immediate aftermath" of the World Trade Center attacks. He said: "The terrorists knew that they could be detained indefinitely and so in many cases they stopped entering the country. It was simple but effective."
The officials described terrorism as a "covert conspiracy" in which family and friends of terrorists were oblivious to their activities and that the only way to counter the threat was to "develop tactics to subvert the threat". The evidence gathered by MI5 and the police in such circumstances cannot be used in court because it would compromise future intelligence-gathering operations and the human sources who helped to supply the information. In the cases of 12 foreign nationals being detained without charge by the British authorities, intelligence on their activities was revealed to the Special Immigration Appeal Commission, a court with powers to deport or detain terrorist suspects. The 12 suspects are being held under the 2001 Anti-terrorism, Crime and Security Act in Belmarsh and Woodhill prisons. When they are freed, they are likely to be held under house arrest.