As British anti-terror police interrogated 11 Pakistanis on Friday over what Prime Minister Gordon Brown called a "major terrorist plot", security sources have indicated that at least three quarters of terrorist plots under investigation in the UK have their roots in Pakistan.

While Afghanistan was seen as the training ground of terrorists in the aftermath of the September 2001 attacks, recent experience has shown that an increasing number of al-Qaeda extremists are being trained across the border in the tribal areas in north west of Pakistan.