Most of Britain’s Islamist Terrorists Came From Highly Segregated Muslim Districts

British Islamist terrorists are getting younger and an increasing number had no prior convictions or previous criminal records before carrying out an act of terrorism or being arrested in the later stages of planning attacks, according to a major report to be published this week in London.

The rising proportion of militants who are so-called “clean skins,” previously unknown to the authorities, has jumped sharply, posing a growing challenge for Britain’s security services as they scramble to try to prevent acts of terrorism, says the report’s author, Hannah Stuart, an analyst at The Henry Jackson Society, a British research group.

Between 1998 and 2010 more than three-quarters of Islamist terrorists were known to British authorities in one way or another well before their arrests, 48 percent had come under surveillance by Britain’s domestic intelligence agency MI5. But the number of terrorists known to authorities has plunged between 2011 and 2015, the proportion known to MI5 more than halved.