Joshua was born in Hampton, England to Martin and Jessica Herdman. He is the youngest of four boys. He started acting when he was about seven. His father is an actor and got him an agent. He got his big break when he auditioned for "Harry Potter and the Sorcerer's Stone" and got the part of Gregory Goyle. In his spare time, he enjoys going back home to Hampton, spending time with friends and family, reading and writing.