Even though he is not accused of supporting militant groups or violence, the British authorities believe it is only by cracking down on activists like Butt and denying a forum for their ideas to be widely heard that the threat posed by jihadis and groups such as Islamic State can be countered.

But critics, ranging from civil rights groups to leading academics and lawmakers, say what the government is trying to do amounts to a curb on free speech which could drive a wedge between the authorities and Britain‘s 2.8 million Muslims