Two more arrests were made today by detectives investigating the murder of Hampton teenager Jamil Palmer.
A 15-year-old girl and a 16-year-old boy were arrested on suspicion of murder and taken to a north London police station for question.
Five people have now been arrested in relation to the fatal stabbing.
On May 6, the day Mr Palmer was murdered in Crane Park, an 18-year-old man and a 16-year-old boy were arrested on suspicion of murder.
Both have been bailed pending further enquiries and are due to return to police early next month.
Yesterday a teenage boy, believed to be 15, was also arrested on suspicion of murder and remains in police custody.
Yesterday detectives called for witnesses to abandon "misguided loyalty" to help bring justice to former Hampton Junior School, Teddington School, Richmond College and Kingston College student Mr Palmer.
Detective Chief Inspector Noel McHugh, of the homicide and major crime command, said: "Jamil was attacked in Crane Park shortly before 3.30pm and the park would have been busy with people.
"Some witnesses have come forward to assist us with our investigation but I am certain there are a number of other people who have yet to speak to us.
"It is clear that there is a misguided loyalty where some people are not speaking to the police, protecting those involved.
"I would ask those who are reluctant to come forward to do so, so Jamil and his family can get the justice they deserve."
Anyone with information should call the incident room on 020 8785 8099 or call Crimestoppers anonymously on 0800 555 111.