A teenage actor who is to appear in the new 'Harry Potter' film was stabbed to death Saturday during an early morning barfight.

Robert Knox, 18, was murdered outside the Metro bar in southeast London as he tried to protect his brother Jamie, 17, from a man with a knife.

The attack, which left three other people with serious stab wounds, took place just a few miles from where Jimmy Mizen, a 16-year-old altar boy, was murdered two weeks ago while trying to shield his older brother.

Knox's parents, Sally and Colin, paid tribute to their son in a statement.

“Rob was kind and thoughtful and would always help out others; he would always spend his last penny on other people instead of himself,” they said.

"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 his family and friends.”

Knox, who overcame bullying as a child to break into acting, had just finished filming a small part for 'Harry Potter and the Half-Blood Prince,' which is due in theaters in November. He plays a Ravenclaw student called Marcus Belby.

An unidentified 21-year-old man was arrested in connection to the stabbing.

Knox is the fourteenth teenager to be violently killed in London this year.

Click here for more from the Sunday Times of London.