Heartbreaking reason Harry Potter cast wore white ribbons at movie premiere

When the star-studded cast of Harry Potter rocked up to London's Leicester Square in July 2009 to celebrate the release of the sixth magical blockbuster, spectators could not deny that the mood was unusually somber.

Being that the colossal list of high-profile actors had met on the red carpet on countless occasions - many of whom having formed close bonds and strong friendships with one another during their time on set - fans of the films expected the cast to relish the opportunity to commemorate their latest achievement together.

Sadly, however, after many stars appeared downcast, attendees went on to notice that the large majority of them were wearing white ribbons on their wrist.

The entire cast wore white ribbons on their wrists. (Jon Furniss/WireImage)

Unknown to many fans at the time, the move was a tribute to their late cast-mate Rob Knox, who had every intention of joining his colleagues on the red carpet that night, but was murdered in a knife attack a year prior, before Harry Potter and the Half-Blood Prince was released to cinemas.

In 2008, just days after finishing filming his scenes, 18-year-old Knox was killed while attempting to protect his younger brother during a night out in London.

The promising young movie star played student Marcus Belby in the franchise's sixth movie, and had signed a contract to appear in the subsequent two films, Harry Potter and the Deathly Hallows Pt I and Part II.

Tragically, before he had a chance to reprise the role, a bar brawl in Sidcup fatally escalated after another group of drinkers began antagonising his 17-year-old brother.

In response, Rob stepped in to intervene, only to be stabbed to death by 22-year-old Karl Bishop.

Knox had signed up to reprise his turn as Belby in the final instalment of the film series. (Warner Bros)

As a result, Bishop was found guilty of the promising young actor's murder and handed a life term with a minimum 20-year sentence before parole would ever be considered.

"I do not think it is proved that you intended to kill Robert Knox," Mr Justice Bean said at the time.

"The truth is that you simply could not care less whether you killed him or not. Your lack of regret let alone remorse was truly chilling."

Hundreds of tributes to Rob poured in from family, friends and fans of the magic movie franchise.

One of whom was Bonnie Wright, who played Ginny Weasley in the franchise. The star told press on the night of the premiere that the Harry Potter family had planned to honour Rob's life with the sweet ribbon gesture.

Bonnie Wright explained the meaning of the white ribbons to press that night. (Mike Marsland/Getty)

"We wanted to wear a white ribbon wristband as a mark of respect," she said at the time. "It is also a tribute to anybody who has been the victim of a senseless, stupid, tragic crime like this. There have been too many."

Daniel Radcliffe - who played the titular role in the film adaptations of JK Rowling's best-selling books - also said: "Rob's death was absolutely tragic. I can't pretend to be his best friend but I knew him and I liked him and it was a terrible shock."

He continued: "He was one of those guys who was liked by everyone who came into contact with him and his death casts a huge shadow."