Two men have been arrested on suspicion of murdering a 15-year-old boy 12 years ago.
Billy Cox was shot dead in his bedroom in Fenwick Place, Clapham, on Valentine's Day in 2007.
He was found bleeding heavily by his younger sister, Elizabeth who was then aged 13 and had returned home from school.
There was no sign of forced entry into the house and detectives have always believed that Billy knew his killer.
On Tuesday two men aged 26 and 31 were arrested on suspicion of his murder and taken to a police station in south London to be questioned.
The breakthrough comes just months after police launched a new appeal in connection with Billy's murder.
A CCTV image of Billy during his final hours was released and showed him walking with two males. A £20,000 reward has also been offered.
The force said the men were detained "following developments within the investigation".
Officers from the Metropolitan Police did make arrests in June 2007 during the original investigation into Billy's death - four for suspected drug dealing and one on suspicion of murder - but no charges were brought.
Billy's father Tommy, who has since died, said in a statement at the time: "We are missing Billy so much. He was not perfect but he was dearly loved as a son and brother."
He added: "If you have anything to say, tell the police, we need to catch my boy's killers."
There were suggestions around violent crime at the time that it was the result of "damaged families" however this was not the case with Billy.
He lived at home with both his parents, who were both described as hard working, with his father employed as a builder.
His friends, who spoke to ITV News London at the time, said they believed he was targeted because he "wasn't the strongest" and people "wanted to hate him for no reason".
Anyone with information can call police on 020 8785 8286, tweet @MetCC, or call Crimestoppers anonymously on 0800 555 111.