The three investigators

Robert Arthur Knox (21 August 1989 – 24 May 2008) was an English actor who portrayed the character of Marcus Belby in the film Harry Potter and the Half-Blood Prince, and had signed to appear in its sequel Harry Potter and the Deathly Hallows – Part 1. Having studied at Beths Grammar School, Bexley, Knox began acting aged 11, gaining small roles in British television shows like The Bill, After You've Gone and Trust Me, I'm a Teenager. His first cinematic appearance was as an extra in King Arthur (2004). Knox died after being stabbed outside a bar in Sidcup, Southeast London, in May 2008, when he intervened in a fight to protect his brother. His murder attracted widespread attention in the British press, and his assailant, Karl Norman Bishop, was subsequently sentenced to life imprisonment, with a minimum 20-year non-parole period.