I left the project feeling hopeful... It's possible to be that extreme and that far gone and turn around
– Deeyah Khan
As the national ceremony takes place to remember those who died in the Paris attacks, many people will be asking what drives extremists to kill people.
We speak to documentary maker Deeyah Khan who has spent two years talking to disenfranchised young men to understand their motivation.
In the making of her film Jihad, Deeyah spent two years with some of the most influential and controversial figures in the British and Western jihadi movement of the past three generations. She meets one of the founding fathers of the British jihad, Abu Muntasir, who went abroad to fight, and who promoted extremism to thousands of young Muslims across the UK and the West. Now a reformed and moderate imam, he is tormented by his violent past. He fought in Afghanistan, Kashmir and Burma, and organised arms shipments.