Clare Smith, Samuel Guidera's girlfriend, told ITV News that she often thought about him lying in the street, in the moments after he was stabbed.
She is urging anyone who knows his killers to come forward:
" The people responsible have been able to move on with their lives get jobs, get married and have children but for Sam's family and friends life has stood still.
"I constantly think about him lying on the street alone without anyone to comfort him and ask his killers or anyone who knows who they are to put themselves in my place."
Officers will be at the scene of the attack near Penge East Station tonight handing out leaflets as part of the renewed appeal for information.
More top news
CCTV and images show man suspected of trying to set the north London mosque alight in alleged Islamophobic hate crime
Detectives investigating a man's body washed up on the shores of the river have arrested a second man on suspicion of murder.
Keepers have the celebrating the arrival of the western lowland gorilla to 22-year-old mother Effie in captivity at the zoo.