Police are offering a £15,000 reward over the murder of Jamil Palmer who was stabbed to death in Crane Park in Hanworth.
The 18-year-old of Belgrade Road, Hampton was killed in broad daylight near Evans Grove in Hanworth, at about 3.30pm on May 6.
Detectives investigating the murder are asking for information which will lead to the arrest and prosecution of the person or people responsible for his death.
Officers also appealed to the community to help find teenager, Mahamed Barre, 17, a Somali male of slim build, who they are looking to speak to in relation to the murder.
Police have released an image of Mr Barre and said he had an "altercation" with Mr Palmer earlier that day and suffered a head injury for which he may require medical treatment.
Detective Chief Inspector Noel McHugh of the Homicide and Major Crime Command leads the investigation.
He said: "I am seeking help from the local community to help locate Mahamed Barre. I would ask anyone who knows of his whereabouts, or has any information that could assist us, to come forward.
"I also appeal directly to Mahamed Barre to present himself at a police station so this matter can be dealt with."
Anyone with information is asked to contact the incident room on 020 8785 8099 or call Crimestoppers anonymously on 0800 555 111.
Anyone who sees Mahamed Barre should call 999.
Four teenagers, aged 15 and 16, have been previously charged with Mr Palmer's murder.
