Detectives have offered a £20,000 reward for information leading them to a man they want to arrest over the murder of Finbar Sullivan.
Officers are appealing directly to Jordan Asije, 22, or anyone who has information about his whereabouts, to come forward.
Mr Sullivan, a 21-year-old student filmmaker, was allegedly kicked, punched and fatally stabbed in the early evening on Tuesday, 7 April at the Primrose Hill viewpoint in north London.
The Old Bailey was previously told how Mr Sullivan entered the park with a friend before he was said to have been surrounded by a group of suspects.
He was punched and pushed to the ground just after 6.30pm, prosecutor Zara Brawley told the court.
One suspect is said to have kicked and stamped on his head, before Mr Sullivan was then stabbed by another man at "least twice", including a fatal injury to his thigh, the court heard.
Detective Inspector Andy Griffin, who is leading the investigation, said he wanted to make it clear that: "Anyone knowingly assisting Jordan to evade arrest, or harbouring him, may be committing a criminal offence and can expect to be investigated and dealt with robustly."
He said: "Jordan, if you are reading this, I urge you to do the right thing and hand yourself in at the nearest police station."
The detective said that while Asije was not believed to pose a wider threat to the public, he should not be approached.
Three already charged with murder
Three men have been charged with the murder and manslaughter of Mr Sullivan and violent disorder in Primrose Hill; another man has been charged with grievous bodily harm.
In June, Ernest Boateng, 25, Alexis Bidace, 25, and Oliuwadamilola Ogunyankinnu, 27, appeared via videolink from Belmarsh and Isis prisons and denied the charges against them.
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It is alleged Boateng kicked Mr Sullivan, taking out his legs and causing him to fall to the ground before he was stabbed.
Bidace is alleged to have punched and kicked Mr Sullivan alongside Ogunyankinnu.
Another unnamed male, armed with a knife, is alleged to have stabbed Mr Sullivan in the thigh, causing an "unsurvivable" injury.
Another man in his 20s also suffered injuries, though they were neither life-threatening nor life-changing.
Judge Dennis set a further case management hearing on 25 September ahead of their trial on 5 April next year.
(c) Sky News 2026: Detectives hunting man over Primrose Hill stabbing murder offer £20k reward
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