"Christadelphian theology is another clever impersonation of Christianity. It denies the devil's existence as a fallen angel, as well as fiery hell, the Trinity, that Jesus' sacrifice was substitutionary, and it teaches that Jesus had a sinful nature. It is definitely not Christian. Read about the Christadelphians here." - CARM
The Christadelphian sect was founded in 1838 by John Thomas, a London-born physician turned Bible teacher. Like the founders of the Jehovah’s Witnesses, Mormons and Christian Scientists, Thomas believed he alone had found the truth of real Christianity. 
Christadelphianism teaches the same two lies as literally every cult and false religion: they deny the deity of Jesus Christ and preach a works-based salvation. 
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- Christian Apologetics & Research Ministry: Christadelphianism
- What is Christadelphianism at GotQuestions.org.
- Christadelphians at All About Cults.