A teenage actor who was in a Harry Potter film was stabbed to death by a man who made a chilling prediction that he was going to kill someone, a court heard today.

Rob Knox, who plays the character Marcus Belby in the forthcoming film Harry Potter and the Half-Blood Prince, was allegedly stabbed five times while trying to protect his younger brother.

The 18-year-old actor was attacked by Karl Bishop outside the Metro Bar, in Sidcup, Kent, in May of 2008.

Prosecuting attorney Brian Altman said “At the time of this event he had just finished filming and was looking forward to being in the next Harry Potter film.”

Knox had gone to the aid of his brother Jamie, 17, who was also an actor.

"Unfortunately, his courage and his sense of duty were to cost him his life,” Altman said.

The attack came after an incident at the same venue the previous week when Bishop, 21, allegedly made a chilling prediction after claiming that his mobile telephone had been stolen at the bar, the court was told.

“He was heard to say ‘I’m going to come back next week and someone’s going to die’,” Altman said.

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