The arrest of two more terrorist suspects in Scotland underlines the speed of the investigation into the atrocities planned for London and Glasgow. The police and security services apparently had no prior intelligence on a campaign of terror inspired by al-Qaeda; but they have reacted with speed and efficiency in uncovering the terrorist network and following up the very many leads left by the bungled operations.

What they have already found is profoundly disturbing. The use of car bombs to cause indiscriminate civilian casualties is a technique honed in Baghdad to deadly effect. Britain – and no longer just London – must be prepared for restrictions, on car access, parking, movement within city centres and at airports and stations, that will have to stay in place for a long time. Al-Qaeda’s seeming use of “clean skin” terrorists, outsiders of whom the police have no record, will mean that clearing visa applications to Britain will take longer and necessarily inconvenience hundreds of thousands of visitors. And perhaps the most dreadful discovery is that at least two of those arrested are doctors, working in British hospitals and supposedly honour-bound to save lives.

Understandably, the police have not revealed many details about the alleged plotters. The priority must be first to arrest the conspirators and, secondly, to gather enough evidence for trials and convictions. But there is something peculiarly repulsive about the alleged involvement of doctors, even if they were not born and trained in this country. The discovery also gives the lie to assertions that Islamist extremism is the result of poverty, deprivation, injustice or the West’s pursuit of policies in Iraq, the Palestinian territories and the wider Muslim world that are somehow inimical to Islam. This is patently not so. Al-Qaeda has often recruited men who are educated, come from a middle-class background and who, in some cases, have personal experience of Western values, learning and the Western way of life.

What is clear, however, is that this perversion of Islam cannot be written off simply as Wahhabi fanaticism or a Muslim equivalent of liberation theology. It does indeed have its roots in narrow fundamentalism, as those who have been temporarily seized by its spurious religious message have bravely admitted. But it is better understood as a cult, and one that appeals especially to the frustrations and rage of young Muslim men. In earlier times, the social restrictions of conservative societies, especially on relations between men and women, would have been largely accepted by men who had little outlet for their emotions. But in the digital age, the contrast with more liberal societies is quickly apparent and often agonising. The result is a prurient interest in the tawdriest aspects of Western life and a subsequent self-loathing, confusion and misogyny that blames women and Western society for undermining Muslim “purity”. Their frustrations are exploited by the politically ambitious, using causes such as Iraq and the Palestinians as motivators.

‘Items sent as earthquake aid’

Hidden among clothing were goods selected and purchased to support the activities of terrorists, a court was told

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• Pictures: Glasgow airport attack

BACKGROUND

• Brown plans to double 28-day detention limit

• Men in bungled raid say police attacked again

• More than Vigilance

• 'Dirty bomb' mastermind plotted wave of atrocities across Britain

• Jihadi house parties of hate

Older, wiser Muslims understand this dangerous dynamic, but have been too cowed or cowardly to stand up to zealots posing as would-be martyrs. It is perverse of left-wing politicians such as Ken Livingstone to equate the Islamists with social justice and national liberation: they believe in neither. To excuse or even tolerate the intolerant is a denial of all the values that the Left purports to embrace. If Muslims are to denounce the roots of fanaticism, so too must those who would embrace them as neighbours and fellow citizens.