By Dominic Casciani
BBC News home affairs
Earlier this week, five men were jailed for conspiring to build a massive homemade bomb out of fertiliser.
It starts here: Street campaigning and agitation, late 1990s
The plotters made up a cell of Islamist extremists, increasingly dubbed "Jihadis", who believed violence was the answer to the problems which they believed Muslims experience around the world.
These men shared some of the aims - and certainly the methods - of the Al Qaeda leadership. But they were not acting alone - and evidence that emerged during the trial links the men into a broader network of British extremists operating in the UK, Afghanistan and Pakistan.
The plotters were not self-radicalised and autonomous; they did not pick up their beliefs by surfing the web and choosing violence. At the same time, it would be too simplistic to claim that they were directly, and at all times, controlled by a hidden hand from above.
Evidence in fact points to something in between - tight cells of Jihadi activists swimming in a sea of like-minded individuals.
Radical banned group
Understanding the network requires looking at how the men came together.
And at the heart of that story is an organisation called Al Muhajiroun. Now banned and declared disbanded by its founders, in the mid 1990s it was at the heart of radical Islamist politics in the UK.
A key figure was self-declared cleric Omar Bakri Mohammed, a media hate-figure who fled the UK after the 7 July attacks.
Bakri preached that Muslims could never live comfortably with supposed Western values. It was an attractive, simple message to certain angry young men looking for meaning.
Alongside Bakri, but often bitter rivals, there were other propagandists circulating similar messages. Abu Hamza established his own organisation which led to his control of Finsbury Park Mosque. Abdullah el-Faisal, a Jamaican-born convert, travelled as a freelance speaker. Both these men are now in prison.
Al Muhajiroun successfully built a network of followers by agitating and campaigning, in particular outside mosques, in colleges and on the university campus.
It had success in Crawley, where Omar Bakri organised physical training meetings in a hut, Luton, and the East End of London.
Contact with Kashmir
It also set up a branch in New York and eventually, an office in Lahore, Pakistan.
With the majority of the potential British recruits coming from a south Asian background, one of the key issues in Islamist politics at the time was the disputed region of Kashmir.
Omar Khyam, the ringleader of the fertiliser bomb plot, had spent time with one of the "Mujahideen" armed groups fighting for Kashmir after a political awakening in his teens.
Back in the UK, some young men associating with Al Muhajiroun's radical message became closely aligned with fund-raising for Kashmiri militia and other causes such as Bosnia. In 2000, a British man, former Birmingham student Mohammed Bilal, was named as a suspected suicide bomber in Kashmir.
The 9/11 attacks changed everything. For Jihadi activists, Osama bin Laden was elevated to a hero who had taken on America.
When the US took the fight back to Afghanistan, a network of sympathisers around the world immediately refocused on supporting Al Qaeda and Taleban fighters. In the Jihadi worldview, it was a Muslim's duty to protect the Taleban's self-declared "Islamic" state.
One of the first to arrive in Pakistan to help this cause was Mohammed Junaid Babar, the "supergrass" witness in the fertiliser bomb plot trial. A New Yorker of Pakistani descent, Babar had associated with Al Muhajiroun in New York and after the attacks headed to the organisation's office in Lahore. There he found many other British men arriving.
Many of these British men shared an apartment in Lahore. They loosely knew each other through their respective cells in the UK, in particular Luton, Crawley and the East End of London.
Two men in this British network were Londoners Zeeshan Siddique, known by the plotters as "Immi" or "Imran", and Kazi Rahman. Babar alleged in court that "Imran" was asked to become a suicide bomber because he worked on the London Underground. Imran is said to have rejected the idea and his whereabouts are now unknown.
Kazi Rahman is in jail. A senior figure in the East London cell, he was arrested in 2005 in a British police sting after trying to buy weaponry, including rockets to shoot down airliners. This was one of the most successful follow-up operations to the fertiliser bomb plot.
Other men went to the Afghan front. Yasir Khan was a Crawley man who knew Omar Khyam. He died during an American bombing raid on a target in Kabul. His family later denied he was a militant.
Two Luton men, Aftab Manzoor and Afzal Munir, also died in fighting. In 2001, an Al Muhajiroun spokesman initially claimed the men as members before retracting the claim.
The deaths of these men raised questions of how exactly young men from Britain could end up in such positions. Facilitators - people with credibility at both ends - were playing a key role in passing on men.
One alleged facilitator is a Luton man dubbed "Q" in the fertiliser bomb trial. His real name is Mohammed Qayum Khan.
The investigation into Omar Khyam and his plotting emerged from an earlier probe into Q's alleged activities. Mr Qayum Khan has refused to speak to the BBC but has told one newspaper he was only involved in charity work.
But according to evidence in the trial, Q was an exporter of people, cash and equipment. And one of those he is said to have exported was Mohammed Sidique Khan, the ringleader of the 2005 London suicide bombers.
When the bomber was sent to Pakistan in July 2004, he was met at the other end by another facilitator, Salahuddin Amin - one of the men jailed this week. Amin in turn introduced the bomber to Omar Khyam who invited him to join his paramilitary training camp.
Al Qaeda links
So what is the link to Al Qaeda? Higher up the chain, the trial heard evidence about two key figures.
Khyam, Amin and fellow plotter Waheed Mahmood were said in the trial to have developed links to senior Mujahideen figures.
One was a former Luton man known as Abu Munthir, almost certainly a nom-de-guerre. Munthir was described as a senior Mujahideen figure receiving support from the UK. The other was Abd al Hadi al-Iraqi, a senior Al Qaeda lieutenant.
According to supergrass Mohammed Junaid Babar, Omar Khyam openly boasted he was working for Abdul Hadi. Shortly before the jury returned in the fertiliser bomb plot trial, the US announced it had seized Hadi and taken him to Guantanamo Bay.
AN INTERNATIONAL NETWORK EXPLAINED
Most of the detail in this network comes from Mohammed Babar's testimony in the fertiliser bomb plot trial
Babar talked about overlapping cells of extremists in the UK
Propagandists created conditions for radicalisation
Alleged facilitators linked radicalised young men to overseas causes
Babar alleged in court that Q sent 7/7 bomber to Pakistan, where he then met the leader of the fertiliser plot