By JACKIE JESKO and ALEX WATERFIELD

A notorious British protest movement called The English Defense League has declared war on radical Islam, a battle they are taking to the streets in rowdy, often violent protests.

Their founder, Stephen Yaxley-Lennon, goes by the alias, "Tommy Robinson." He claims that his group is not anti-Muslim, but several of his followers have been connected to hate attacks like mosque bombings.

Robinson said the gruesome murder of Lee Rigby was the "tipping point" that spurred the group to rise in prominence. Last May, two knife-wielding Muslim men savagely attacked and beheaded Rigby, a British soldier, on the streets of London in broad daylight, telling eyewitnesses the killing was "an eye for an eye … because Muslims are dying by British soldiers every day."

"Nightline" met with an infamous Islamic preacher named Anjem Choudary and his group of young followers in the streets of London, where they were advocating for Sharia law. Choudary, whose extremist Muslim group was banned under Britain's Terrorism Act, refused to condemn the killing of Rigby.

Several of Choudary's followers take part in so-called "Sharia Patrols" in the streets of London. YouTube videos of these patrols surfaced online and immediately caused public outcry. They show young Muslims speaking out to enforce Sharia law on the streets - harassing a man they believe to be gay, ordering a man to stop drinking and telling a young woman she is dressed immodestly.

When "Nightline" went on a Sharia Patrol, the leader said that they wish for Sharia law to rule the world, and that Muslims should give up any other identity but their religion.

ABC's Lama Hasan, who is a British Muslim, spent time with both Robinson and the Sharia Patrol in London, to get to the heart of conflict between the warring sides. She goes back to the neighborhood of Luton, which is not only Robinson's hometown, but was also the launch point for the July 7, 2005 London suicide bombings, the worst terrorist attack in British history.