MI5 (Britain's domestic intelligence agency) has admitted that Islamic radicalism is no longer growing in the United Kingdom. But many of those who were already radicalized, are still dangerous. This is a similar pattern that MI5 encountered with the (Irish Republican Army). Despite Northern Ireland (which the IRA wants to unite with the Republic of Ireland to the south) being largely free of IRA terrorist violence for the last decade, MI5 still spends 15 percent of its budget seeking out the diehard Irish terrorists, and preventing them from carrying out more attacks.
The Islamic terrorists have now gone from a growing menace, to a persistent one. The rising death toll of dead Moslems, at the hands of Islamic terrorists, precipitated a decline in support, among Moslems, for Islamic radicalism. That led to more tips and cooperation with the police. This put more Islamic radicals on the run. Some of them were so desperate to avoid MI5 that they fled to Northern Ireland, where only one percent of the population is Moslem (versus four percent for Britain overall).
So far, 70 percent of the terrorist plots discovered in Britain have some connection to Pakistan based terrorists. This makes it easier for MI5. About four percent of the British population is from South Asia, or is of South Asian ancestry. Half of those are from India, 36 percent from Pakistan, and most of the rest from Bangladesh. About half the South Asian population is Moslem. While Britain is the European nation most agreeable to assimilation, it is also, like other countries in the region, hostile to migrants. They are tolerated, not welcomed, as they are in the United States. As with the United States, natives, and legal migrants are hostile to illegal migrants.
The Moslem South Asians who cling to their old culture, form a pool of supporters for Islamic radicalism and Islamic terrorists. In the past, European nations considered their unhappy migrants as a potential source of criminals. Now, some of those criminal minded foreigners are turning to Islamic terrorism. But the speed with which MI5 has identified Islamic terrorists, and police have arrested them (and courts have sent them away for life) has discouraged many Moslems from getting involved with Islamic radicalism.