Police divers were dredging a canal today after a tip-off that a gun used to murder two people almost five years ago was dumped there.
Jordan Jackson, 20, and Leyla Djemal-Northcott, 21, were killed at a flat in Menlo Gardens, Upper Norwood, south east London, on March 7, 2006.
Masked men, who detectives believe were targeting Mr Jackson and his brother Keiran, burst in and fired at least six shots.
Mrs Djemal-Northcott died as she lay in bed and Keiran Jackson was lucky to survive a gunshot wound.
Police search teams have begun work at the Regent's Canal where it crosses Mile End Road at Mile End Park in Tower Hamlets, east London.
Detective Chief Inspector Neil Hutchison, of the Met's Trident unit, said the gun could hold the key to the murder.
He said: "This happened nearly five years ago but I am hopeful that someone may come forward with information in relation to these murders.
"Allegiances may have changed in the last five years and any information could help us to finally bring those responsible to justice.
"If anyone out there is reluctant to tell us what they know because they are frightened then I want to assure them that they will be protected."
Mrs Djemal-Northcott's mother, Christine Djemal, said: "Leyla has not had the opportunity to finish college, get married, have children.
"She is deeply missed by her family who still find it hard to come to terms with her sudden and violent death."
The Met is offering a reward of up to £20,000 for information which leads to the arrest and conviction of those responsible for the murders.
:: Anyone with information should call police on 0208 247 4553 or Crimestoppers, anonymously, on 0800 555 111.