The ringleaders behind the cartoon-row demonstration in London include a British-born radical who underwent military training in Afghanistan, The Independent on Sunday can reveal.
This paper has learned that the protesters included Abdur Rahman Saleem, a former member of the now-disbanded Al-Muhajiroun sect, which has been linked with terror and intimidation.
The 32-year-old from Ilford in Essex, who also goes by the name Abu Yahya, has denounced the Queen as an "enemy to Islam" and boasted that he helped recruit Britons to be trained abroad for the Islamist cause.
The fanatic, who is now involved with a new group called Ahl ul-Sunnah Wa al-Jamma (ASWJ), is understood to be among at least a dozen extremists being investigated by Scotland Yard after the placard-waving protest earlier this month.
Police have been examining 60 hours of video footage from CCTV cameras outside the Danish embassy in London to gather evidence for the Crown Prosecution Service in connection with threats made of beheadings and bombings. Officers have now prepared a file detailing public-order offences including causing harassment, alarm and distress.
However, the agitators are unlikely to face the more serious charge of incitement to murder. A senior Metropolitan police source said: "We are looking into complaints that were made about the offensive placards and submitting a file to the CPS. But it would be far fetched to expect anyone to take it seriously if someone has a placard saying cut off the head of the cartoonist."
Publicly, Muslim leaders have dismissed the Danish embassy agitators as hotheads who distort the teachings of the Koran. But privately they admit they are concerned about the sinister influence of groups such as ASWJ and Al-Ghurabaa, whose website calls for Muslims to kill those who insult the Prophet Mohamed.
These British-born haters of Western society are guided by Sheikh Omar Bakri. He is the cleric blamed for radicalising young Muslims who have gone on to take part in international terror attacks, a charge he denies. Barred from ever returning to Britain, Mr Bakri, 47, is currently in exile in Lebanon but is in regular contact with his followers in this country. He was the spiritual leader of Al-Muhajiroun before it was disbanded.
The cleric had a strong following in Luton, which is where the bombers involved in the 7 July atrocities met before catching their train to King's Cross. Al-Muhajiroun was banned from the town after being accused of trying to intimidate Muslims into not voting in the general election.
On 24 February, one of its off-shoots, Al-Ghurabaa, is planning to hold its own demonstration outside the Israeli embassy in London calling for Muslims to wage jihad against the country.
One of Mr Bakri's most committed followers is Anjem Choudary, 38, a solicitor who, like Abu Yahya, was involved in orchestrating the Danish embassy demonstrations and who describes Mr Bakri as "a great man". The graduate of Southampton University is evasive about how many members the new offshoots of Al-Muhajiroun have, but claims that at least 1,000 Muslims share their views.
In an interview with this paper, Mr Choudary also said that groups like Al-Ghurabaa and ASWJ represent "true" Islam and the views of the new generation of British Muslims, who are more radicalised than their parents. Denying that police have contacted him about the protest, he said he did not think there was anything wrong with the placards.
"You either have people who protect Islam or you don't," said Mr Choudary. "There are always going to be people who are upset, but banners saying behead people should not be taken seriously."
However, religious leaders have condemned the radical groups for stirring up hatred towards the West and urged police to prosecute them.
The Muslim Council of Britain has also called for tough measures to be brought against those who incite others to violence. "Prior to 7 July we did just dismiss them as ignorant troublemakers but after July it becomes a lot more difficult to make that judgement," a spokesman said.