CCTV footage of two men running near a murder scene could be vital to solving a six-year-old case, police have said.

The footage was uncovered by detectives investigating the stabbing of Greenwich University student Samuel Guidera – who was on his way to meet his girlfriend.

Mr Guidera, 24, a history and politics student, was found collapsed near Penge East station, Sydenham, at about 9.55pm on February 12, 2011.

Police today, Monday, February 13, released two clips showing the two men run past the scene following the attack – before returning about 15 minutes later.

A full review of all CCTV cameras in the area saw that the footage was unearthed.

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Detective Chief Inspector (DCI) Chris Jones, who leading the investigation, said: "This is still very much a live investigation. We hope that this previously unreleased CCTV may lead to the identification of two people that may be able to assist our investigation.

"Or it may be the two people in the CCTV recognize themselves and contact us. I would say to these two people, please do contact us, no matter what information you have, it may be crucial to solving this case.

"It is still hoped that after six years someone with knowledge of what happened to Sam can come forward and help solve the case.

"For the parents of Sam; Sarah and Chris, it is still as raw for them today as the day Sam was killed, and the investigation team will ensure there is no stone unturned in the search for Sam's killer or killers."

Mr Guidera was stabbed in the heart. His wallet containing a Greenwich University student card was stolen from him. This has never been found.

On the night of his death he had travelled on the 9.17pm train from Bickley to Penge East, arriving just after 9.30pm.

He crossed the footbridge over the railway to the Newlands Park exit as he was on his way to meet his girlfriend.

The 24-year-old was last seen, before being found stabbed, at a bus stop opposite Bailey Place shortly before 9.40pm.

His mother and father, Sarah and Chris Guidera, in statement said: “We just want somebody out there who knows something that could help in the apprehending of the killers to come forward so they do not have the opportunity to take another person's life and destroy another family.

“It could be somebody reading this who gets the call about the savage death of a loved one next.”

Detectives have spoken to nearly 900 witnesses during the course of this investigation, and have eliminated more than one thousand leads.

DCI Jones added: “Even after six years there are still some enquiries ongoing into the numerous lines of enquiry instigated in the case.”

Anyone with information is asked to contact the incident room on 020 8345 3734 or police via 101 or via Twitter @MetCC.

To give information anonymously call Crimestoppers on 0800 555 111 or visit crimestoppers-uk.org.