What triggers fatal attraction?

In just two and a half weeks, London has become unusually jumpy.

Twitchy passengers are suddenly on the look-out for clammy-looking young men with bulging rucksacks who might conceivably be Islamist extremists, a description which given the July heat seems to fit a sizeable proportion of travellers.

Grim tales float up from underground, of fleeing, unsuccessful bombers dangling stray wires, choking smoke and panic.

Last week, however, before the second wave of attempted attacks, Bashir Ahmad, the uncle of Shehzad Tanweer one of the bombers behind the July 7 explosions told the News of the World that Shehzad "was driven to that [the bombing] by desperation, because he couldn't find justice anywhere''.

Later, he also informed the Evening Standard that "there are injustices in this world and some people feel more strongly about it than others. Shehzad obviously fell into that category''.

The notion that the British Muslim suicide bombers of July 7 were spurred on by some passionate form of public-spiritedness, of course, is both flagrantly idiotic and deeply dangerous.

Ahmad's comments will do little to make life easier for his own family or the beleaguered families of the other suicide bombers, who have condemned the attacks in unequivocal terms.

Yet Ahmad's apparent reasoning that his nephew was compelled to kill himself and seven innocent people near Liverpool Street station by a combination of righteous anger and sheer desperation at injustices suffered by fellow-Muslims is not too distant from the explanations that have in the past been provided for Palestinian suicide bombers by non-Muslim British public figures.

Jenny Tonge, the former MP for Richmond Park, was sacked from the Liberal Democrat front bench last year when, following a trip to Palestine, she remarked of Palestinian suicide bombers: "I think if I had to live in that situation and I say that advisedly I might just consider becoming one myself.''

Cherie Blair, speaking to reporters after a charity event with Queen Rania of Jordan in 2002, also mused: "As long as young people feel they have no hope but to blow themselves up, you are never going to make progress.''

In both cases, the women analysed suicide bombing as an almost inevitable by-product of extreme hopelessness. Both Baroness Tonge's and Cherie Blair's comments caused a ripple of controversy at the time, and then were forgotten.

I wonder, however, if the recent apparition of British suicide bombers raised in circumstances that were far from desperate might have caused Baroness Tonge and Cherie Blair to reconsider the psychological ingredients they once naively deemed necessary to the phenomenon.

For both women have appeared to confuse the motivation of suicide with that of a suicide bombing.

Suicide, in which the victims annihilate only themselves, is certainly the product of severe depression and hopelessness.

Suicide bombing, however, fired by a volatile combination of religious and political fervour, is a vigorous act of self-assertion: the bomber hopes to make his triumphant, bloody mark upon the world before proceeding to his reward in Paradise.

It is no accident that the bulk of suicide bombers are young men, a group particularly drawn, not necessarily to hopelessness, but to the potent romance of a "cause''.

They are easily bored by the dreary, complicated business of living peacefully: the dull job, the squalling baby and the round of minor compromises.

Their professed desire to "avenge injustice'' is not their driving motivation: that is a palatable excuse to buoy up their self-image. The real spur is an arrested, adolescent craving for immortality and legendary status among their peers.

Few sane people would deny that many Muslims worldwide have suffered injustices, although those injustices flow as frequently from the hands of their fellow-Muslims as from Christians or Jews. One does not need to be a Muslim to be concerned by their suffering.

But let us be under no illusion that Islamist suicide bombers, whether they immolate themselves in a Haifa restaurant or the London Underground, have any love for justice: they murder the most vulnerable without compunction. Nor have they any protective instinct for their fellow Muslims.

Britons of all religions should remember one thing in the difficult months to come: the more we indulge spurious justifications for mass murder, the less we honour our dead.