20 Harry Potter Actors Who Are No Longer With Us

10. Robert Knox - Marcus Belby

Like Legeno, Robert Knox died in tragic circumstances well before his time.

Knox appeared only briefly in the series as Marcus Belby in The Half-Blood Prince (though he was set to appear in the follow-up), which was set to be his big break in the industry. Belby was a Ravenclaw who was recruited to Professor Slughorn's Slug Club because of his famous father.

Tragically, just days after filming his role, Knox was murdered outside of a bar in London when he stepped into a fight to protect his brother and was stabbed. His remorseless killer, Karl Bishop, is serving a life sentence for the crime.