MI5 head Jonathan Evans said Wednesday prosecutions have reduced risk. But Europe's siding with Israel on Gaza may incite European Muslims to hostility.
Bilal Abdulla received life in prison for a 2007 attack on the Glasgow airport and a foiled plot against a London nightclub.
Police have arrested the head of Indian Mujahideen, which claims responsibility for recent bombings.
The trial, which ended Monday, highlights key differences between US, British counterterrorism approaches.