Britain's domestic spooks, the MI5, revealed last month that they've foiled five terror attacks since the horrific 7/7 subway-bus bombings in London in 2005. That's great news. But now they're tracking 30 new plots, involving 200 cells and 1,600 people in the United Kingdom -- mostly of Pakistani origin, according to the Fimancial Times.

Of course, those are just the plots they know of . . .

Worse, British intelligence said they believe that al Qaeda is regrouping in Pakistan, which could put the United Kingdom -- because of its substantial South Asian ties -- at significant risk of more terrorism.

And MI5 doesn't believe that Britain is al Qaeda's lone target by any means: It could easily be a stepping stone for Pakistani-originated/assisted terror attacks elsewhere, including in the United States (still al Qaeda's No.1 mark), Canada and continental Europe.

We've already had a close call on that nightmarish front: Last summer's plan by home-grown, U.K.-based al Qaeda acolytes to bring down 10 or so U.S.-bound airliners over the Atlantic using liquid explosives, could've killed as many or more people as the 9/11 plot.

That plan, too, had ties into Pakistan. Plus, it was even nastier than originally thought: They didn't plan to destroy the airliners over the Atlantic, but over U.S. cities -- to kill as many as possible.

Then there's Dhiren Barot -- the Pakistan-trained British convert to Islam. Considered al Qaeda's top U.K. operative, he was convicted last month for plotting to blow up the New York Stock Exchange and other sites with help from Osama's Pakistan crowd.

Radicalized by local imams, British recruits head to Pakistan for training. Once schooled in terror, al Qaeda's new foot soldiers return home, staying in touch with their Pakistani al Qaeda contacts who either encourage terrorism -- or direct it.

MI5's director general summed it all up in a November speech: "What we see at the extreme end of the spectrum are resilient networks, some directed by al Qaeda in Pakistan, some more loosely inspired by it, planning attacks including mass-casualty suicide attacks in the U.K."

Britons make over 400,000 visits a year to Pakistan. That large volume of travel makes the United Kingdom vulnerable to penetration by not only al Qaeda, but to the Taliban or other Pakistani terrorist groups such as Jaish-e-Mohammed and Lashkar-e-Tayyiba, who are all increasingly chummy.

Throw in the fact that, per public-opinion polls, at least 100,000 Britons (presumably Muslims) believe the 7/7 attacks were justified -- it's enough to give MI5 permanent insomnia.

The plucky Brits are doing all they can to prevent another terrorist attack -- MI5's boosted its casework by 80 percent since January. But that's not a direct answer to the Pakistan problem.

Bad enough that Pakistani President Pervez Musharraf eased off the Taliban a few months ago, resulting in a 300 percent increase in attacks across the border in Afghanistan. Now al Qaeda is blossoming in the same lawless tribal regions that the Taliban uses to stage those raids.

The question has become unavoidable: Is Islamabad serious about fighting extremism and terror?

True, Pakistan has made invaluable contributions to combating al Qaeda over the past five years, capturing scores of key leaders and providing tips that led to the foiling of deadly plots, including this summer's attempted airline bombings and the Barot arrest.

And, yes, Musharraf took a political risk in late October, OK'ing the Predator missile strike against the compound thought to be hosting al Qaeda No. 2 Ayman al Zawahiri for dinner. (It missed him by just hours.)

But the facts on the ground indicate that Musharraf's policy in the tribal areas isn't undermining the Taliban or al Qaeda -- and may be facilitating their resurgence.

Pakistan needs to do more to fully deny these, indeed, all, terrorist groups the use of its territory. As long as it fails, both Pakistan and the rest of the world will pay a hefty price.