Evidence of a leading Muslim extremist calling for the beheading of British Muslim soldiers has been uncovered.A video of Abu Izzadeen, preaching his message of hate two years ago, has been discovered on an underground website.In the video, he said: "Whoever allies himself with the Kaffirs (non-believers) against the believers - he is one of them."He who joins the British Army, the American Army, he is a mortal kaffir and his only hukum (punishment) is for his head to be removed."Indeed, whoever changes his deen (Muslim code of life); kill him."© Independent Television News Limited 2007. All rights reserved.