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.
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The 20-year-old was found fatally wounded on Roth Walk, near Finsbury Park, north London at around 3am on Saturday, Scotland Yard said.
Police have arrested a man wanted in connection with a burglary at the home of pensioner Richard Osborn-Brooks.
The rally comes after it emerged that the Home Office destroyed thousands of landing cards documenting the arrival of windrush-era migrants