Media playback is unsupported on your device Media caption Gordon Corera looks at whether radical preacher Anjem Choudary prompted the government's anti-extremism proposals

Anti-extremism proposals announced by the British government on Wednesday are widely seen as targeting individuals like radical Islamist preacher Anjem Choudary, who is seen as an influential figure in the UK. Research from the US, as well as an investigation by the BBC, suggests his influence also extends across Europe.

Torill Karlsen walks through the park in a quiet Norwegian town where she used to take her son, Thomas Alexander.

It was just over a month ago that she received a phone call telling her that he had died - killed while fighting for the group calling itself Islamic State, in Kobane, Syria.

"When I got the message that he was dead, the blood just froze to ice in me," she says.

"I think of him every day, every second, every minute. I feel that it's very meaningless that my boy should go to Syria from this little town and be dead there."

'Laughing stock'

Torill believes the police could have done more to act on concerns about him.

But when asked who was responsible for him going to Syria, she blames the Norwegian group called Prophets Umma.

That group is believed to be behind many of those who have travelled from Norway to fight in Iraq and Syria.

Image copyright AP Image caption Islamic State fighters have taken over swathes of Iraq and Syria

Youssef Bardo Assidiq became involved with the people that set up Prophets Umma but became disillusioned.

He now works to de-radicalise people and turn them away from violence.

"I remember the group back in 2012, everyone laughed at them," he said.

But they soon became more professional.

He believes Anjem Choudary had a "huge impact" on the group.

"He knows the law. He knows where the limits are.

"And he also knows how to run an organisation and that is something these guys didn't have a clue about.

"We have seen from the first meeting with Anjem Choudary here in Norway, the group has evolved drastically. So they have got a lot more dangerous."

'Going underground'

The spokesman for Prophets Umma met me in a central Oslo hotel.

Ubaydullah said he had been to Britain last year to meet Mr Choudary.

"I respect him because of his knowledge and we talk from time," he told me. "Of course I learn a lot of things from him. And he also gives us some advice."

The Norwegian Security Service is aware of the challenges of people travelling to Iraq and Syria.

They say they are sure about 75 people have gone there, of whom 26 have returned and 16 have been killed.

But they also say they believe the real figures are much higher.

They say there are strong indications that the flow has been organised by people belonging to the group Prophets Umma.

However, they are unsure that banning it is necessarily the answer.

Image caption Torill Karlsen's son went to fight in Syria

"Banning a group would very often result in that group going underground or being less visible but it doesn't mean that the problem would go away or that the motivation would go away," says Jon Hoffmann, director of strategic analysis at the Norwegian Police Security Service.

"Some might be motivated to leave or not join it if it were criminalised.

"But for others the effect could be the opposite."

Groups in Belgium, the Netherlands, Denmark, Spain and elsewhere are all believed to have contact with Mr Choudary.

Research by the Western Jihadism Project, at the US's Brandeis University, suggests Mr Choudary's influence extends well beyond Norway when it comes to people going to fight in Iraq and Syria.

"By my estimate, based on my studies of Western Europeans who have gone to fight, about a third, if not more, are members of these affiliates, these groups," says Jytte Klausen who leads the study.

"And they haven't been shy about proclaiming their membership because the affiliates of Anjem Choudary groups are not banned in most Western European countries."

Figures disputed

Mr Choudary himself disputes the overall figures.

He says he has visited many European countries and says he has had contact with 40 or 50 countries around the world.

But he told the BBC that these groups were not formally set up or run by him or linked to him.

He also denies sending people to fight.

"I don't think there's one example of anyone in Iraq, Afghanistan or Syria, or any place in the world, whether passed away or whether alive today, who has actually said that I'm here because Mr Choudary asked me to go abroad or I was incited or encouraged by him to go abroad," he says.

Anjem Choudary is currently on bail in the UK on suspicion of membership of a banned organisation but has not been charged with any offence.

Countries across Europe, it seems, are trying to work out how to deal with radical groups who are careful in what they say and do but are nonetheless highly influential.

And many of them, it seems, are connected in some way to Mr Choudary in Britain.