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Entertainment • Actor

Robert Knox (actor)

Robert Arthur Knox, known as Rob Knox, was an English actor born in Kent in 1989.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Robert Arthur Knox, known as Rob Knox, was an English actor born in Kent in 1989. He is best known for playing Marcus Belby in *Harry Potter and the Half-Blood Prince* and had been cast in the next film before his death in 2008. He died after being stabbed outside a bar in Sidcup, London, while intervening in a fight to protect his brother.

Early life and career

Robert Arthur Knox was born in Kent, England, on 21 August 1989. He began acting at a young age and appeared in small television roles and an early film appearance before being cast in the Harry Potter film series.

Harry Potter role

Knox played Marcus Belby in *Harry Potter and the Half-Blood Prince*, which was released posthumously in 2009. He had signed to appear in *Harry Potter and the Deathly Hallows – Part 1* but died before filming could continue.

Death

Knox died on 24 May 2008 after being stabbed outside a bar in Sidcup, London. He was intervening in a fight to protect his brother when he was attacked. The murder drew significant media attention in the United Kingdom.

Legacy

An annual memorial film festival, the Rob Knox Film Festival, was created in his name by the Rob Knox Foundation. The foundation supports arts training for young people.

Key facts

  • He portrayed Marcus Belby in *Harry Potter and the Half-Blood Prince*.
  • He had signed to appear in *Harry Potter and the Deathly Hallows – Part 1*.
  • He began acting at a young age and appeared in British television productions before his film role.
  • He was stabbed to death in Sidcup, London, in May 2008 while trying to protect his brother.
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Canadian context

His story is widely known to Canadian Harry Potter audiences because *Harry Potter and the Half-Blood Prince* was released and distributed in Canada as part of the franchise.

Frequently asked questions

Who was Robert Knox?
Robert Knox was an English actor best known for playing Marcus Belby in *Harry Potter and the Half-Blood Prince*.
What was Robert Knox's most notable role?
His best-known role was Marcus Belby in *Harry Potter and the Half-Blood Prince*.
How did Robert Knox die?
He was stabbed to death outside a bar in Sidcup, London, in May 2008.
Was Robert Knox in more than one Harry Potter film?
He appeared in *Harry Potter and the Half-Blood Prince* and had been cast in *Harry Potter and the Deathly Hallows – Part 1*.
Why is Robert Knox remembered?
He is remembered for his Harry Potter role and for the public attention surrounding his death, as well as memorial efforts in his name.

References

  1. Wikipedia — https://en.wikipedia.org/wiki/Rob_Knox
    Supports: Birth name, birth and death dates and places, Harry Potter role, death circumstances, conviction, and memorial festival.
  2. Apple TV — https://tv.apple.com/us/person/robert-knox/umc.cpc.2o8ba1hjkxnmd8ogj3m2ga147
    Supports: Acting background, school, early roles, and casting in Harry Potter films.
  3. IMDb — https://www.imdb.com/name/nm2527061/
    Supports: Known-for credit, family relation mentioned in biography, and death circumstances.
  4. People — https://www.people.com/harry-potter-actor-robert-knox-killed-murderer-showed-no-remorse-8746527
    Supports: Summary of his death, role, and later reporting on the murder case.