Anti-terrorist experts are floundering about trying to understand Islamic suicide bombers in the UK and the rest of Europe.
The experts came together and argued together at a conference in London organised by the Centre for Defence Studies at King's College and the Norwegian Defence Research Establishment.
The conference sought to assemble "the puzzle that will help us better understand what determines and motivates the actions of individual jihadists."
The puzzle however remained frustratingly in pieces.
One major argument was about the issue of psychological profiling. This seeks to understand the motives of one group of terrorists in order to predict who might be the next.
I believe the psychological profiling of Islamic terrorists is a complete waste of time Dr John Horgan University of St Andrews
To a layman it sounds quite reasonable - and indeed there was a fascinating analysis of the 7/7 London bombers - but it came under sustained attack from one of the speakers, Dr John Horgan, a psychologist at the University of St Andrews, which has specialised in anti-terrorist studies.
"I believe the psychological profiling of Islamic terrorists is a complete waste of time," he said.
"It will not work. It means different things to different people and there is the wrong assumption that if we can identify the traits of known terrorists we can move into predictions.
"The terrorists are not a homogenous population and we simply do not understand why some move from legal activities to illegal."
"Too much is based on a limited range of people and we are seeing only the tip of the iceberg."
I asked Dr Horgan afterwards what should be done instead.
Social profiling
"Psychological profiling is beguiling," he said. "Social profiling, looking at the social background, is more useful.
"It's also important to look at the ways in which a person gets drawn into terrorism and from that to develop counter -terrorism strategies. There is an "IED" progression, from involvement to engagement and then, in some, to disengagement from terrorism.
"At points along this line, we can try to stop them. For example in Northern Ireland, the racketeering that went on in paramilitary groups was exposed. That undermined the idealism of some who thought they might join."
'Al Capone approach'
Others at the conference suggested the "Al Capone" approach, in which the financial dealings of activists could be targeted.
Despite Dr Horgan's comments, there was a good deal of profiling on display at this conference.
Peter Nessen of the Norwegian Defence Research Establishment had analysed the London suicide bombers and came up with a typology, which, he said, provided important lessons.
He identified four types of terrorist in the four young men who blew themselves and others up:
the entrepreneur
the protégé
the misfit
the drifter.
'Sense of injustice'
The entrepreneur, or leader, was Mohammed Siddique Khan. This figure, said Peter Nessen, is the crucial one, who makes things happen. He is often an idealist as Khan was. Khan had an "activist mindset." He had been active in protests on behalf of the Kashmiri community before. He had a strong sense of injustice on behalf of Muslims around the world.
"But this figure often needs contacts with a radical imam for religious guidance and, for practical purposes, contacts with the jihadi infrastructure, though instructions can also be got from the internet," said Nessen.
The second figure, the protégé, he identified in this group as Shezad Tanweer.
"The protégé might be younger and certainly looks up to the leader. He is also activist minded, also educated and is sometimes skilled. He might be used for bomb making. Tanweer went to Pakistan with Khan in 1994, so was close to him."
The third type, the misfit, was Hasib Hussain.
The misfit, according to this theory, is someone with a troubled background, not an idealist. He joins because of personal problems, which he thinks will thereby be solved. He might even join out of loyalty to his friends. He is streetwise but not well educated and might have violent tendencies.
The fourth type, the drifter, was said to be Jermain Lindsay.
"This kind of person drifts into the group through circumstances or contacts. He might not have been an activist before and might not be entrusted with key details of the group's activities," said Nessen.
The lessons, Nessen said, were that there were different ways into terrorism, that the role of the "entrepreneur" was crucial, but that this was not enough. There had to be connections outside the group, to religious leaders and jihadi structures.
Converts
We were also given a glimpse into the phenomenon of converts, some of whom, like the shoe-bomber Richard Reid, then went onto to violence.
Alison Pargeter, of King's College pointed to similarities between 34 converts she had identified. They were often fragile individuals from deprived and broken homes, looking for a way out. They were also vulnerable to influence as they were not able to distinguish between moderate and more extreme branches of Islam and were drawn into "purer" forms from which the leap to violence was easier.
As for social profiling, there was an interesting account of the background in Spain, which suffered in the Madrid bombs in 2004.
Professor Fernando Reinares of the Elcano Royal Institute in Madrid, said that, unlike the situation in the UK, there was no mature second or third generation of immigrants in Spain yet, so most of the 188 jihadists arrested since 2001 had been from abroad, mostly Morocco and Algeria. The Spanish authorities were now looking closely at the influences on the upcoming generations.
Professor Reinares also pointed out the problems of prediction and said the Madrid bombers were very varied, with both university graduates and illiterates in their ranks.
I felt that the conference rather ignored some of the political influences on suicide bombers, like the world events -Afghanistan, Iraq, the Middle East, Chechnya, Bosnia and others - that provide a basic motivation for many of them.
In one off-the-record session there was a reference to this from a contributor who did call for a better Western approach on a global scale, arguing for patience and a clear human rights framework for policies.
Perhaps this was felt to be too intangible for such a meeting. Certainly some of the policemen there were more interested in what they could do in practice.
'No silver bullet'
One of them, Chief Inspector Mick Gillick of West Midlands police, who works with Muslim and other communities in his patch, said there was "no silver bullet."
"I am a little bit sceptical about profiling being the answer to predicting terrorism," he told me, "though I recognise the concept of the entrepreneur. However, because Khan became a terrorist after being an activist, it does not follow that other activists will become terrorists.
There will be more bombers Michael Taarnby Danish Institute for International Studies
"I know that intelligence agencies these days are looking "upstream" to see who might be shaping up as suspects, but my role is to develop relations with the communities and this is vital because they will be the ones who tell us if something is suspicious."
One speaker who had made a grimly successful prediction was a ZDF German television journalist Elmar Thevessen. He made a documentary in 2004 about a possible attack on the London Underground.
The German authorities were on high alert because of the World Cup this summer, he said, worried because a jihadist pamphlet called "The Unfulfilled Duty" had recently appeared.
It was, unusually, written in German, not Arabic or English, a sign that those behind the pamphlet were now appealing to young people who were deeply embedded in German society.
Michael Taarnby of the Danish Institute for International Studies, who has analysed jihadists across Europe, predicted what everyone fears.
"There will be more bombers," he said.
