A £20,000 reward has been offered in a bid to trace a van that may be central to an investigation into the murder of French student Amelie Delagrange.
The van could now be lawfully owned by a member of the public
Police have also released a new image of the white van on the eve of the first anniversary of her murder on Twickenham Green in south-west London.
Ms Delagrange was attacked on 19 August 2004, possibly by a serial killer.
Detectives believe the Ford Courier van, registration P610 XCN, was used by her killer and could hold vital clues.
To date, no-one has been charged with Ms Delagrange's murder.
A 36-year-old man arrested in November was bailed until next month.
Det Ch Insp Colin Sutton said the suspect is thought to have driven the van to Twickenham Green, parked, got out, attacked Ms Delagrange and then driven off.
After that, the van may have been sold on and be lawfully owned by someone else or could have been scrapped or burnt out, he said.
The vehicle pictured in the stills taken around May last year in Hillingdon, west London, was registered to Cargo Air Services in Heathrow.
Officers discovered the van was likely to have been used by Amelie's killer about four weeks after her death but it was another couple of months before it had been identified from a list of 25,000.
Amelie Delagrange came to London to improve her English
Mr Sutton added: "Locating it is of such vital importance to us that we have taken the unusual step of linking its recovery to the offer of a substantial reward for information leading to a prosecution."
He said it was possible the murder weapon had been left in the back and forensic tests could be carried out.
He added he also needed to identify a small group of people who were nearby that night.
"We have no suspicion that any of these people were involved in the murder, but it is possible that they still have small pieces of information," he added.
Mr Sutton said he remained confident that the 22-year-old's killer would be caught.
Ms Delagrange died of severe head injuries following the attack. She had earlier spent the night at Cristalz wine bar in nearby London Road.
Her murder has been linked with six other attacks in the area, including the killing of 19-year-old gap-year student Marsha McDonnell in nearby Hampton and the attempted murder of former convent school head girl Kate Sheedy.