They are two countries thousands of miles apart, but the ties that bind Britain and Pakistan are stronger than most. History, empire, trade, immigration, literature, even cricket: the traffic - commercial, human, and cultural - between the two has strengthened every decade since Pakistan was carved out of British India in 1947.
But in the wake of the London bombings, these ties are coming under enormous strain. Within days of the 7/7 attacks, Britons were quick to seize on a reported Pakistan connection. Three of the four suspects were of Pakistani origin. Two had visited the country recently and are thought to have been radicalized in madrassahs, or Islamic schools, there.
And The New York Times reports that one of the suspects may have met with two known Pakistani militants at an official training camp north of Islamabad.
In Britain, there is frustration and helplessness over the suspicion that a former colony could be serving as a school for would-be terrorists.
In Pakistan, meanwhile, there is indignation and resentment at being blamed for acts committed by Britons in Britain. Beneath it all lurk some of the racial and cultural misunderstandings left over from the colonial era.
"This might well drive a wedge between the two countries," says Vernon Hewitt, an expert in South Asia at Bristol University, in southwest England.
"What is dawning on the British government is that the state institutions of President [Pervez] Musharraf can't really put very much pressure on a civil society that has become very Islamicized," he adds. "I don't think he can crack down on [madrassahs]. It would create such domestic unease that his regime could not withstand it."
Musharraf has acted aggressively in recent days to demonstrate his resolve in confronting radicals. The president, once viewed as illegitimate in Britain because he came to power in a 1999 coup, recognizes that his support for the war on terror since 9/11 has improved his relations with the West dramatically.
Last week his security forces rounded up 300 religious extremists, raiding madrassahs and detaining clerics. But none of those detained has been directly linked to the London events. Instead, there were ranks of militants from two militant groups, the banned Jaish-e Muhammed (the army of the prophet Muhammad) and Lashkar-i Tayyaba.
Rules were added preventing banned extremist groups from reforming under new names, cracking down on "hate literature" and requiring all madrassahs to register by year-end.
But Musharraf was careful to emphasize that fighting terror was not a job for Pakistan alone. In an address to the nation, he said that while Pakistan had a problem, "England has a problem also.
"There is a lot to be done by Pakistan internally. And may I suggest there is a lot to be done in England also."
Musharraf claims that Pakistan's antiterror efforts over the past four years have borne fruit. On Monday, he said that Al Qaeda was too weak to organize terrorist attacks from Pakistan, claiming to have "eliminated their command system there."
Pakistan has indeed nabbed several key Al Qaeda lieutenants, including operational mastermind Khaled Sheikh Mohammed in 2003 and Abu Faraj al-Libbi earlier this year.
It says it has passed vital intelligence to Britain, helping to foil previous attacks, notably one just prior to the British election in May. Indeed, cooperation at the intelligence level has been noteworthy. When Pakistani agents picked up alleged Al Qaeda computer whiz Mohammed Naeem Noor Khan in Lahore last year, it quickly led to arrests in Britain.
"These events have really brought us closer to each other," says Abdul Basit, a senior Pakistani diplomat in London. "They have reinforced our mutual commitment to fight this scourge of terrorism."
Yet observers note that Musharraf has to be careful how robustly he squeezes the radicals in his midst. Militants have been very useful to Pakistan in projecting policy, fighting the Soviets in Afghanistan in the 1980s, for instance, and serving on the front lines of Kashmir for decades.
Musharraf, moreover, would probably alienate large chunks of Pakistan's fiercely Islamicized society if he does not act deftly.
"General Pervez Musharraf is caught in a dilemma," says Ayaz Amir, an analyst and columnist for the respected Dawn newspaper. "On the one hand he must show that he is serious about so-called religious extremists and on the other he does not have the political legitimacy to order a real crackdown against the forces of religious extremists."
That much is evident from the streets of Pakistan, where clerics and some political leaders are incensed at being targeted in the wake of the London bombings.
"There is no military training in madrassahs, but launching a crackdown against the religious institutions and dubbing Muslims as terrorists are perceived as a conspiracy against the whole Muslim ummah [global Islamic community]," says Prof. Ghafoor Ahmed, deputy chief of the country's largest Islamic party, Jamaat-e Islami.
That view may gain credence when the identities are known of the four bombers who tried to execute copycat attacks on the London transit system last week. Early indications are that the men may have west or north African connections. If so, it would weaken the tenuous link between terror in Britain and teaching in Pakistan.
"Linking London bombing with Pakistani madrassahs is only part of a broader campaign and conspiracy against madrassahs," says Maulana Sami ul Haq, head of the Dar-ul Uloom Haqqania school at Akora Khattak, a refugee-camp-turned-town near the western border with Afghanistan.
Pakistan's flirtation with Islamicization really took root during the Soviet occupation of neighboring Afghanistan, when tens of thousands of mujahideen were sustained by Pakistan's security agencies, with covert CIA backing. After 1992, they remained either to fight in Kashmir or to strengthen Islamic parties in Pakistan.
But ties with Britain are subject to a different historical backdrop. On the positive side, the vestiges of empire have left a legacy of trade (Britain is the second largest investor in Pakistan), cross-cultural influence (from Pakistani literature in Britain to English sports in Pakistan), and migration (700,000 Pakistanis living in Britain).
Cultural misunderstandings persist, however. Strident voices in Britain still question why British-born Pakistanis support Pakistan, not England, in cricket matches. Few would ask the same question of an Australian living in Britain. That mistrust has sharpened since the bombings. Nearly two-thirds of Britain's 1.6 million Muslims have considered leaving the country, a Guardian/ICM poll shows.