“They can give this family justice and peace of mind if only they’ve got the courage to come forward and tell us what they know.”

These are the words of Det Ch Insp Dave Whellams, the officer in charge of Champion Ganda’s murder investigation.

Like the teenager’s mother, he believes answers lie with Champion’s friends, and that they are refusing to come forward.

But he has a message for them.

“There are measures we can put in place to protect them,” he said. “If anybody is in a position where they are fearful of repercussions, they just need to come and discuss it with us and we can explain what we can do.”

Ten men have been arrested since Champion was killed in May, but no one has been charged.

“People out there know who’s done it and don’t want to cooperate with the police,” Mr Whellams reiterated. “They don’t wish to be seen as a ‘grass’, informant or ‘snitch’.

“The information that we believe a couple of people have is vital, but there’s a misplaced ‘loyalty of the streets’.

“There are indications that the parties believed to be involved are associated with particular gangs.

“We have a number of suspects in mind, and we’re working towards a certain group of people.”

He added: “I would urge anybody who has information relating to the murder of Champion Ganda to contact the incident room and speak to us directly, or speak to Crimestoppers if they wish to give the information anonymously.”

Call the incident room on 020 8345 3775, or dial 0800 555 111 and speak in confidence to Crimestoppers.