Thousands of young Muslim men are attending meetings in east London every week run by a fundamentalist Islamic movement believed by Western intelligence agencies to be used as a fertile recruiting ground by extremists.
Tablighi Jamaat, whose activities are being monitored by the security services, holds the tightly guarded meetings on an industrial estate close to the area where some of the suspects in the Aug. 10 terror raids were arrested.
Last week it emerged that at least seven of the 23 suspects under arrest on suspicion of involvement in the plot to blow up transatlantic airliners may have participated in Tablighi events.
The organization -- influenced by a branch of Saudi Arabian Islam known as Wahhabism -- has already been linked to two of the July 7 London suicide bombers who attended a Tablighi mosque at the organization's headquarters in Dewsbury, northeast England. The jailed shoe bomber Richard Reid is also known to have attended Tablighi meetings.
Until now, the leaders of Tablighi Jamaat -- which means "group of preachers" -- have refused to open their doors to outsiders, shrouding the organization in mystery.
Tablighi enthusiasts say that the organization, founded by a scholar in India in the 1920s, has no involvement with terrorism and simply encourages Muslims to follow the example of the prophet and proselytize the teachings of the Koran. As one sympathetic imam put it, they were the "Jehovah's Witnesses of Islam."
Last Thursday evening, we witnessed around 3,000 men from as far afield as Great Yarmouth (eastern England) and the Isle of Wight (southern England) stream through the back streets to the Stratford meeting.
There, at the gates of a seemingly derelict industrial site, men in fluorescent jackets waved those who are known to the Tablighi Jamaat hierarchy under a security barrier, and into one of three fields that surround a cluster of prefabricated buildings which form a temporary mosque.
As we entered the complex one person spoke admiringly about the "main man" for the southeast division of Tablighi Jamaat.
"We can't call him a prophet," he said. "No one can be a prophet. But when you meet him you'll realize. He's helped a lot of people in the area to follow the right path, the path of the prophet. He'll talk to you openly this evening and everything will make sense."
Seconds later, the main man stood next to his red van in Islamic dress and a smart blue waistcoat as hundreds of men, many carrying suitcases and sleeping bags, filed past him into a network of six rooms cobbled together with planks of wood and corrugated plastic windows.
The largest room was reserved for the main speaker, an elder from Preston (northwest England) who spoke in Urdu. His sermon was relayed through a microphone to five other rooms in which interpreters provided simultaneous translation into English, Arabic, Sinhala, Turkish and Somali.
Thoom heaved as a sea of faces, white, black and Asian, spilled into the hallway. Most were teenagers and men in their 20s and 30s dressed in Islamic dress, caps and beards. Some came in suits and ties, others in jeans and hoodies. There were old men too, who weaved slowly through to the front of the room, and a few young boys.
The main man took a seat in the middle of the room to interpret proceedings. The murmur of hundreds of whispering voices stopped as he put on his headphones.