Rob Knox (right) was protective of his younger brother
A teenage actor who had a part in the forthcoming Harry Potter film was stabbed to death as he tried to protect his brother, a court has heard.
Rob Knox, 18, was stabbed five times outside the Metro Bar, in Sidcup, south-east London, in May last year.
He was protecting his 17-year-old brother Jamie from Karl Bishop who was "running amok", the jury was told.
Mr Bishop, 21, of Sidcup, denies murder and five charges of wounding with intent to cause grievous bodily harm.
Brian Altman QC, prosecuting, said of the young actor: "Unfortunately, his courage and his sense of duty were to cost him his life."
The stabbing followed a row at the same venue the previous week after which Mr Bishop allegedly made a "chilling" prediction, the Old Bailey jury heard.
Mr Altman said: "He was heard to say, 'I'm going to come back next week and someone's going to die'."
The defence claims that Mr Bishop, of Carlton Road, Sidcup, was acting in self-defence.
Mr Knox, of Swanley, Kent, had just finished filming the role of Marcus Belby in the forthcoming film Harry Potter and The Half-Blood Prince.
Mr Altman said: "A few minutes after midnight on May 24 last year, Rob Knox was stabbed to death by this defendant, who was running amok outside the Metro Bar.
"At the time, Bishop was armed with two quite ordinary but two quite lethal knives which had come from his kitchen and with which he had quite deliberately armed himself."
He added: "Tragically, in the melee, Rob Knox lost his life.
"Rob was just one of a number of young people who, over the past year or so, have fallen victim to knife crime in London.
"He was particularly unfortunate because he fell victim to a young man who was not only an habitual knife carrier but also someone who would quite happily deploy and use knives as weapons, two in this case, to settle scores.
"That is precisely what happened here."
Mr Altman said both Rob and his brother were interested in drama and had parts in a film about King Arthur.
He said that Mr Knox was a "popular young man" and was "especially protective" of his younger brother.