LONDON (AFP) - Police in London have been given more time to question a 21-year-old man held on suspicion of fatally stabbing a teenager actor who played a role in the forthcoming Harry Potter film, Scotland Yard said on Monday.
Rob Knox, 18, was killed outside the Metro Bar in southeast London in the early hours of Saturday morning while reportedly trying to protect his brother from a man wielding a knife.

The teenager played the role of student Marcus Belby in “Harry Potter And The Half-Blood Prince”, which is due to be released in November.

Police arrested a 21-year-old on suspicion of murder and have been given more time to question him, Scotland Yard said on Monday, without giving further details.

Knox’s murder takes to 14 the number of teenagers violently killed in London this year, a figure which has caused alarm among police, politicians and campaigners.

The stabbing took place after a man entered the bar and was seen waving two knives around. A scuffle broke out and Knox and his brother Jamie were reportedly trying to protect each other.

Several others sustained knife wounds.

Tom Hopkins, 18, and Tarik Ozress, 17 - both of whom are friends of the Knox brothers - managed to pin the man down after wrestling with him for several minutes before police arrived.

Hopkins, who was stabbed in the head, said: “Rob was just trying to help out. He was like that. I grabbed the knife, I didn’t know at the time that he had another knife. It was just chaos.”

Knox was taken to hospital where he was pronounced dead.

Friends said there had been a row over a phone last week and believe it could have been a revenge attack.

“Rob was kind and thoughtful and would always help out others,” the teen’s parents Colin and Sally said in a statement. “The life and soul of the party, he was very outgoing, loved sports, and would always strike up a conversation with people.

“He was respectful to others and adored by all his family and friends.”

Film producers Warner Bros said: “We are all shocked and saddened by this news and at this time our sympathies are with his family.”