Were they inspired by Al Qaeda magazine? Authorities investigating whether terrorists were spurred into action by publication which urges 'lone wolf' attacks

The Woolwich terror attack has chilling echoes of a previous plot to kidnap and behead a British Muslim soldier.

Five men were jailed in 2008 after police smashed a Birmingham-based terror cell’s plan to burn a kidnapped soldier’s body and parade his head on a stick as a warning to other Muslims against joining the British Army.

Thankfully, ringleader Parviz Khan failed to identify a soldier to target before they were detained by the security services.

Khan had links to Al Qaeda in Pakistan and said in a conversation bugged by MI5: ‘Like that, I think you cut it off like you cut a pig. Then you put it on a stick and we say, this is to all Muslims man want to join the Kuffar (non-believer) army - this is what will happen to you.

‘Then we throw the body, burn it, send the video to the chacha . The chacha can release it there. These people gonna go crazy.’ The words of Khan, jailed for life, were an ominous warning.

Last night, as armed police guarded two men suspected of killing and trying to behead a soldier near Woolwich barracks, detectives were urgently trying to establish how the killers were radicalised.

Officers were checking jihadi websites where preachers of hate urge Islamic extremists to behead soldiers. The authorities will also be investigating whether the attackers had been spurred into action by reading Al Qaeda’s English-language magazine, Inspire.

The publication is produced by Al Qaeda in the Arabian Peninsula and contains exhortations to carry out so-called ‘lone wolf’ terrorist attacks by self-motivated groups and individuals.

Articles and ‘jihadi advertisements’ have urged people to carry out attacks with knives and to run people down in vehicles.

The Boston Marathon bombers used instructions contained in the first issue of the magazine to build and detonate their devices. The guide was called ‘How to build a bomb in the kitchen of your mom’.

Inspire has been linked to at least 15 terrorism cases and Al Qaeda made an abortive attempt to publish the 11th issue of the magazine just days ago.

It is believed that intelligence agencies intervened in the publication process, meaning that the file was blank when people who downloaded it tried to open it. A previous issue was doctored so a section on bomb-making was replaced with cupcake recipes.

Documents such as Inspire are circulated on a network of websites which are attracting large audiences. A recent survey suggested the ten leading websites linked to Al Qaeda have 125,000 registered members between them and may be attracting as many as 250,000 visits per day. The network is currently circulating a new English magazine produced by the Pakistan Taliban, which calls on supporters in the UK to murder teenage human rights campaigner Malala Yousufzai.

Another possibility, which will be considered by counter-terrorism officers, is that the minds of the killers of the British soldier were poisoned in a mosque or even in prison, an increasingly popular recruiting ground for groups linked to Al Qaeda.

It was not clear whether the men were on the intelligence radar of the security services or were ‘clean skins’, not known to police.

Some witnesses claimed the soldier was beheaded but there was no immediate confirmation of how he died. What is not in doubt is that he suffered a terrible knife attack. The head and the sword have a specific place in the rhetoric, heraldry and history of Islam. There is no shortage of passages in the Koran that jihadists can interpret to support their propaganda.

Chapter 47, Verse 4, is a favourite of those with evil intentions: ‘When you meet the unbelievers (in battle), smite their necks until you have crushed them . . .’

Jihadists have used this as justification for the scores of beheadings of non-believers in Iraq.When the word ‘behead’ is typed into Google, the search engine automatically suggests completing the sentence with ‘those who insult Islam’ - suggesting this is the most common search term beginning with that word.

The attack in Woolwich is one of several attempts to kill soldiers and MPs.

Student Roshonara Choudhry became a heroine in jihadi circles for stabbing MP Stephen Timms during his constituency surgery in Beckton, East London, in May 2010. Mr Timms survived.

A cell of terrorists from Luton was jailed last month at Woolwich Crown Court for discussing an attack on a Territorial Army barracks with a bomb attached to a remote controlled car.

Three weeks ago six men pleaded guilty in the same court to planning an attack on an EDL rally in Dewsbury, West Yorkshire, using machetes and sawn-off shotguns and a home-made bomb.

Placards calling for anyone who insults the prophet Mohammed to be beheaded were waved during an angry protest in London in 2006. One man, Mizanur Rahman, who carried a placard that said ‘Behead those who insult Islam’, was later found guilty of inciting racial hatred.