<p>The Government Communications Headquarters, Britain's electronic eavesdropping centre popularly known as GCHQ identified some of these terrorists. The centre, based in Cheltenham, Gloucestershire, intercepted telephone calls made by British militants at a training camp in the tribal borders of Pakistan to identify the suspects.<br /><br />According to The Sunday Times, some are said to come from the Rochdale area, others from the Midlands. Matching their voice prints allowed the security services to trace their connections to other individuals in their network.<br /><br />"GCHQ is doing a lot of significant work in spotting these guys and helping the Americans deliver the drone kills," said a source with knowledge of the agency's work. An important aspect of this work is the analysis of voice prints, a technique that can identify a voice speaking on a telephone in Afghanistan or Pakistan by matching it against a databank of suspects held by GCHQ.<br /><br />"You pick up a voice and if you find a match for it in the database, you can get a name. Then you get the call data and see who the guy has been calling," one expert said. The method was apparently used to pick up "credible" intelligence of the plan for simultaneous attacks by British and foreign insurgents against several European cities.<br />An Mi5 surveillance operation began tracking potential suspects in London and northwest England earlier this year.</p>
<p>The Government Communications Headquarters, Britain's electronic eavesdropping centre popularly known as GCHQ identified some of these terrorists. The centre, based in Cheltenham, Gloucestershire, intercepted telephone calls made by British militants at a training camp in the tribal borders of Pakistan to identify the suspects.<br /><br />According to The Sunday Times, some are said to come from the Rochdale area, others from the Midlands. Matching their voice prints allowed the security services to trace their connections to other individuals in their network.<br /><br />"GCHQ is doing a lot of significant work in spotting these guys and helping the Americans deliver the drone kills," said a source with knowledge of the agency's work. An important aspect of this work is the analysis of voice prints, a technique that can identify a voice speaking on a telephone in Afghanistan or Pakistan by matching it against a databank of suspects held by GCHQ.<br /><br />"You pick up a voice and if you find a match for it in the database, you can get a name. Then you get the call data and see who the guy has been calling," one expert said. The method was apparently used to pick up "credible" intelligence of the plan for simultaneous attacks by British and foreign insurgents against several European cities.<br />An Mi5 surveillance operation began tracking potential suspects in London and northwest England earlier this year.</p>