Each year, hundreds of thousands of Pakistanis who hold British passports travel to Pakistan to see family and friends. Some, however, sneak off to terrorist-training camps in Pakistan's remote and uncontrolled tribal areas.

So what's to keep these terrorist-trained Brit-Paks, as they are known, from using their passports to board a plane to the U.S.? That is one of the disturbing issues Con Coughlin raises in the Telegraph today.

British Prime Minister Gordon Brown acknowledges his security services are tracking 20 active terror plots at any one time. Many, Coughlin writes, involve "‘Brit-Paks' who have been radicalised and trained in Pakistan and managed to return undetected to Britain."

All of this points attention back on Pakistan and the depth of its commitment to curtail the use of its land to train jihadists. It is promising just such a crackdown in the wake of last month's Mumbai terrorist attacks:

"But just as Islamabad promised to work closely with Washington after the September 11 attacks, and the British government following the July 7 bombings, the Pakistani government's ability to deliver on its promises is highly questionable, leading to some within the West's security establishment to ask whether the Pakistanis are really serious about rooting out the terrorists.

The reason successive Pakistani governments have struggled to mount an effective campaign against Islamist terror cells is the country's all-pervasive Inter-Services Intelligence agency (ISI), which created most of the terror groups in the first place. Al-Qaeda was the product of the ISI's support for Islamist radicals fighting the Soviets in Afghanistan in the 1980s, while LeT was created by ISI to pressure Delhi into relinquishing control of Kashmir."

The question is what happens if more attacks are found to have roots in the Pakistani tribal areas and if such attacks hit Britain or the U.S.