Joseph was born in Oxford in 1974. When he was 16 his parents split up and he moved into a caravan to live by himself. He graduated from Bristol's Old Vic Theatre School in 2002, after winning a scholarship place, and got his big break four years later when he starred in groundbreaking production Soundproof, a contemporary thriller which brought together deaf and hearing actors. Joseph contracted a virus when he was 16 which caused partial hearing loss. He appeared in popular TV series such as Dalziel And Pascoe, Silent Witness and historical drama Dunkirk, before landing the role of Captain Harville in 2007's Persuasion and Tim in gritty Channel 4 drama Clapham Junction. In 2008 he was cast as Jesus in the BBC mini-series The Passion.