A growing number of young Muslim men in Britain want to train to become suicide bombers, a BBC investigation has revealed.
Omar Bakri's home has previously been raided by anti-terrorist police
On a drizzly Friday night in an old church in London's East End about 60 young men sit wrapped up against the cold.
While others head for bars and nightclubs, these members of the radical Islamic group, al-Muhajiroun are about to hear a lesson entitled: "The virtue of the self sacrifice operation".
It is a rhetoric their spiritual leader, Omar Bakri Mohammad, has been especially asked to give.
"People like to call it suicide bombing," he says. "We call it self sacrifice. You must fight for the way of Allah - to kill first and be killed."
Young Muslims take notes on laptops while others scribble down key phrases and children as young as nine sit, mesmerised.
Despite his avuncular demeanour, Bakri, who came to the UK from Beirut, has twice been arrested for issuing a fatwa - one of them on the former Prime Minister, John Major.
Tonight, he rallies the crowd by listing places in America, Africa and the Middle East where suicide bombers have already struck, before coming closer to home: "If somebody decided to land an aeroplane over 10 Downing Street, for example - this is a form of self sacrifice", he tells them.
As al-Muhajiroun's worldwide leader, Bakri has taken his tutorials to branches across the UK. It was in Derby that Omar Sharif, the son of a well respected local businessman, asked Bakri for private meetings.
Last year, Omar's body was found washed up on an Israeli beach. He had gone to Tel Aviv with Londoner Asif Hanif who blew himself up outside a bar, killing three people.
But the deaths have not deterred Bakri's other students who see the Tel Aviv bombing as an act of martyrdom.
Hassan Butt, a confident 24-year-old from Manchester, told me he is one of hundreds of Britons who has been to a military training camp in Pakistan.
He says some may now be fighting or already dead - but others could be waiting, as he is, to put their fighting skills into practice while holding down 9-to-5 jobs in the UK.
"You will be patient and you will persevere and maybe if you are accepted into that network of fighters you, too, will get an order."
A spokesman for the Muslim Council of Britain, however, told us the influence of groups like al-Muhajiroun is exaggerated.
But Patrick Mercer, Conservative Shadow Homeland Security spokesman, believes Bakri and his followers should be accused of sedition.
"It's likely that from this evil preaching up and down the country, one or two suicide bombs will emerge."
File On 4: BBC Radio 4, Tuesday 10 February at 2000 GMT, and repeated on Sunday 15 February at 1700 GMT.