British police Friday thwarted a car-bomb attack that would have brought carnage to the streets of London just days before the second anniversary of the July 7, 2005, bombings that claimed 52 lives. The car was packed with nails, gas canisters and petrol containers, and left outside a nightclub near Piccadilly Circus. This latest attempt to kill and maim hundreds of civilians is most likely the work of al Qaeda or one of its numerous British-based affiliates. It was timed to coincide with the departure of Tony Blair, and the entrance of new Prime Minister Gordon Brown. It also coincided with Blair's appointment as the Quartet's new Middle East envoy in the face of strong opposition in the Arab world.

In the coming months, the al Qaeda network and its allies will seek to test the strength and resolve of the new British government, as well as the fledgling prime minister, whom they may well see as a weaker figure than Blair. They will attempt to intimidate both British public opinion and the nation's political leadership into withdrawing from Iraq, and scaling down Britain's close alliance with the United States.

In recent years, Britain has become a hornet's nest of Islamic extremism. The domestic intelligence service MI5 is currently investigating 30 major terror plots in the U.K., and has over 1,600 individuals under surveillance, who are operating as part of 200 British-based terror networks. In April, British courts convicted an Islamic terror cell of attempting to kill thousands of shoppers at the U.K.'s largest shopping mall, in Bluewater, Kent. Between September 2001 and December 2006, there were 1,166 terrorism-related arrests in the U.K., with over 400 people charged.

The scale of the problem involving young Islamic extremists in Britain was highlighted in a major 2005 British Foreign Office/Home Office study. Terrorist organizations such as al Qaeda have found a fertile hunting ground in the U.K., where half of Muslims are under the age of 25, and where there is widespread opposition to the U.S.-British-led war on terror. The report revealed that extremist groups are secretly recruiting well-educated affluent Muslims from British universities, in addition to impoverished, underachieving Muslims through mosques and prisons. Former MI5 director general Eliza Manningham-Buller estimates that over 100,000 British citizens consider the July 2005 London attacks as "justified."

Friday morning's foiled attack underscores that Britain remains in a state of war, and is a central front in the global war against terrorism. New Prime Minister Gordon Brown must demonstrate courage, resolve, and determination in the face of a mounting threat. Indeed his own legacy as British leader may be defined ultimately by his ability to deal with the most important issue of our time -- global terrorism and its support by state sponsors such as Iran and Syria.

It is imperative that Brown not show any sign of weakness as leader. He must make a commitment to increasing British defense spending, and be willing to project British power military on the world stage, wherever British interests are threatened. Like Blair, Brown will have to demonstrate his abilities as a war leader, at a time of great threat to British and international security.

Domestically, he must do everything possible to deal with the terrorist threat. Greater powers must be given to British authorities to monitor, detain and extradite suspected terrorists, and the U.K. should immediately withdraw from all articles and protocols in the European Convention on Human Rights that might act as a barrier to effective anti-terrorism measures. Ultimately, Britain should withdraw from the Convention altogether, and reassert national sovereignty in this critically important area.

The U.K. must not tolerate the Islamic militancy in its midst, which seeks to destroy British society and impose a Muslim state. Foreign Islamic clerics who preach treason and violence should be deported and banned from reentering the country. Britain also clearly needs a new generation of Muslim leaders, untainted by association with, or sympathy for, Islamic extremism and who are proud of their British identity. They must be willing to condemn terrorism unequivocally in all its forms, and help root out extremists from Muslim communities.

On the world stage, the new British government must not allow al Qaeda and its allies to dictate British foreign policy, as they have succeeded in countries such as Spain. Brown should not agree to an artificial timetable for the withdrawal of British forces from Iraq, and remain committed to increasing British troop strength as part of the NATO-led operation against the Taliban in southern Afghanistan. He must also stand up to Iranian intimidation in Iraq, and send a clear message that there are military consequences for Iranian-backed attacks on British forces. In addition, Gordon Brown must ensure that the maintenance of the Anglo-American special relationship remain a top priority.

Britain's battle against terrorism must be fought on several fronts, both at home and abroad. The war must be taken to the enemy, including state sponsors of international terror. It is a war that must be fought in conjunction with Britain's closest ally the United States, sending a clear message that the West will not be divided in the defence of freedom.

Nile Gardiner is the director of the Margaret Thatcher Center for Freedom at The Heritage Foundation.