What should we do about radicals?
The number of young Britons travelling to Syria means the authorities are more concerned than ever about countering radicalisation. But how can they deal with people whose views are considered radical? Here are the key approaches.
The government runs a deradicalisation programme called Channel, which targets people considered at risk of being drawn into violent extremism. For the first time, someone on it explains how it works.
"Adam", 28, a Polish Muslim convert, says he had been preparing to train as a jihadist. Before he was identified as having troubling views, he had hoped to travel to Syria to fight.
"I was thinking I've got nothing to lose and I have a lot to win. If I die, if they shoot me or anything, I'm not going to lose anything except my life," he tells the Victoria Derbyshire programme.
The police can step in when people expressing radical views break the law. Benjamin Raymond, 26, is the spokesman for National Action - a new, small, far-right group. He describes himself as a national socialist, or Nazi.
The group has fewer than 100 members but, as a result of its openly racist demonstrations, it has seen about 20 arrests.
But he says police intervention will not deter the group. "Most cases enhance the feeling of persecution and the idea that what we are doing is right."
Some people may find the views expressed in this film offensive.
Anne Marie Waters, from Sharia Watch, often criticises Islam.
She had been organising a Prophet Muhammad cartoon exhibition until it was prevented from taking place by police. She feels she has been silenced.
She says she is not a radical but "simply telling the truth". "If there ever was a time to defend real freedom of speech it is now. People are being killed all over the world over this," she adds.
Abdul Muhid does not have a passport - nor does his wife. He was arrested in September on suspicion of membership of a proscribed organisation. He is now on bail and the passports, as well as numerous other items, were confiscated from his home.
Mr Muhid has friends who have gone to live under so-called Islamic State and believes they have every right to. He is unable to leave the country and says his bail conditions are controlling him.
Radicals are considered useful to the security services as they can use their unique access to groups considered potentially dangerous to inform on them.
One 25-year-old British Muslim said MI5 had tried to recruit him to inform on his community. He says it happened three years ago after he had taken part in a convoy to Gaza and a subsequent trip to Turkey.
The Victoria Derbyshire programme is broadcast on weekdays from 09:15-11:00 BST on BBC Two and the BBC News Channel.
Films directed by Ben Lister.