David Anderson, until last month Britain's independent reviewer of terrorism legislation, says that to defeat the problem, you have to understand it. In London this week a vast new study, the largest of its kind in Europe, will be published that aims to do precisely that.

The report, 18 months in the making and obtained by The Sunday Times, scours court transcripts, media reports and hundreds of other sources to bring together for the first time information on who Britain's Islamist terrorists actually are. It covers all 269 individual convictions or suicide bombings and all the nearly 400 offences involved, from the very first in 1998 to the beginning of last year. It asks: where did the terrorists come from? What influenced them? What kind of neighbourhoods do they live in?

Some of the answers are what you would expect — terrorists are mostly young and mostly male — but the delve into the data also demolishes a great deal of conventional wisdom, and provides important new insights into one of the country's most pressing problems.

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