LONDON - Behind net curtains in solid, red brick family homes in Dewsbury in Yorkshire, four families are asking the question that has Britain transfixed.
How and why were four intelligent young men transformed into Britain's first cell of suicide bombers?
Prime Minister Tony Blair in the House of Commons spoke of "a perverted interpretation of the religion of Islam". He called for tolerance as a public response, deploring the attacks on mosques since the explosions.
In Dewsbury, on the edge of Leeds, native town of the bombers Mohammed Sadique Khan, 30, a primary school teacher with one young child, Hasib Hussain, 18, Shahzad Tanweer, 22, and a fourth man, there were more complex responses.
Even as they acknowledged sadly that these were homegrown British bombers, many politicians and commentators were still looking for "outside" influences, particularly for links to al Qaeda and fundamental Islamists in Pakistan, from where all four families originated.
A powerful handful - among them Dewsbury Labour MP Sahid Malik and his defeated Conservative rival Saheeda Wasir, a vice-president of the Conservative Party - pointed out that there were problems bubbling under the surface of the much-vaunted multicultural British society that community leaders and the police should ignore at their peril.
The death list from last week reads like a League of Nations. But in reality many of the ethnic minorities live in ghetto communities, with virtually no links with others of Britain's racial communities.
Parts of Yorkshire, of Manchester, of Leicester and certainly London are solidly Asian and Muslim.
Images of the continuing war in Iraq and claims of atrocities at Abu Ghraib and Guantanamo Bay in Cuba appear constantly in the mainstream British press - and even more so on radical Muslim websites and newspapers and film distributed through the more radical mosques.
British Muslims have resentments - not least of the pressures that force them to educate their children partly in their countries of origin, in the case of last week's bombers, Pakistan.
Britain has Anglican, Catholic and Jewish state-funded schools, but few Muslim schools that attract state funding, a bitter source of complaint.
As the police in London used mobile phone records, surveillance footage and personal effects including credit cards to piece together the relationships and the last hours of the four men, that question of "why?" was on all lips.
That question produced reactions such as the Evening Standard headline of Wednesday night, "Bomber Was a Teacher".
The naivete with which the question is being posed - but they were educated? but they had no financial problems? - in part sums up the why.
Only one appears to have been a low achiever - and he was sent to Pakistan by his family in the hope that family and religious pressure would steady him.
The religious influences he came under appear to have tipped the balance the wrong way. The others all appear to have spent time in Pakistan, one at least to gain a religious education.
Britain has no shortage in the past 35 years of decently brought up, well-educated terrorist attackers.
The IRA in the 1970s, 80s and 90s in Northern Ireland and on the British and European mainlands recruited through Britain's universities and teacher training colleges, particularly Catholic colleges, for the radicalised and idealistic young, particularly those of families settled in England.
The same reaction, "but they were educated", was repeated frequently.
Mairead Farrell, who was shot by the SAS as she planted a bomb in Gibraltar in 1992, is referred to always as "convent-educated".
The IRA, as with the al Qaeda attackers now, often drew a significant amount of its support from the poor and disaffected, but a lot of its bombers were the well-educated, often from families with no known Irish Republican background.
These innocents, unblemished by any anti-terrorist police records, were ideal bomb planters.
The readiness of the radicalised young to risk life and liberty for an ideal was evident in the UK during the G8 summit last week, which was undoubtedly the reason for the timing of the four suicide bombers' attack.
The protesters spilling through the woods of Stirling in Scotland to block roads around the Gleneagles Hotel, where the leaders of the richest nations were in conclave, were not "foreign anarchists", as the more rabid of Britain's right-wing papers suggested.
They were students and recent graduates, many from Britain's top universities.
The intellectually inquiring elite of their generation - protesting just as the current Foreign Minister, Jack Straw, did in his youth, when he was president of the National Union of Students and a peace demonstrator - historically take direct action.
The difference with the four young men who blew themselves up last week is that they were ready not just to risk a court appearance for disorderly conduct, not even to risk accidental death while planting a bomb, as Mairead Farrell did.
They appear to have set out deliberately to kill themselves.
The police have found no trace of timing devices on their bombs, indicating that they detonated them themselves, knowing they too would die.
On the TV footage of them arriving in London they were relaxed and laughing.
The families in Dewsbury yesterday were saying - in part from behind veils - that they were unable to bear either the pain of what their sons had done or the opprobrium of their neighbourhood.
Shahzad Tanweer had been to Pakistan to study his religion there, but the family had no idea he had become a fundamentalist.
These views were as alien to his family as they are to the majority of most other faiths and of those of no faith. But they were dangerously real to the four bombers - as they are demonstrated to be almost daily in Iraq and in Israel.
People in Britain are coming to terms with the fact that Yorkshire accents do not preclude a fundamentalist readiness to seek death for a cause.