Murder detectives are appealing for friends of a Feltham cleaner to help them piece together the 'missing jigsaw parts' and bring his killers to justice.
Lakhvinder Cheema, 39, who worked for Rentokil, died in hospital early on January 28 after developing symptoms which suggested he had been poisoned.
He and his 21-year-old fiance had been rushed to the West Middlesex Hospital from their Princes Road home the previous evening. She was suffering similar symptoms but later recovered.
Officers believe the pair may have been deliberately poisoned and are appealing for people who knew Mr Cheema to help them piece together the details of his life.
Det Ch Insp Howard Groves, of the Homicide and Serious Crime Command, said: "As part of the investigation we are piecing together details of Lakhvinder's lifestyle so we can ensure all possible lines of enquiry are fully explored."
"We have spoken to Lakhvinder's family and work colleagues but we need more information from friends who knew him on a personal level.
"Often people don't know they have the 'missing jigsaw parts' and think their information is trivial or irrelevant but it could be key to proving a whole case. We're asking anyone who knew him and may have spoken to him in the last few months to come forward and let us judge if their information is useful for ourselves."
A post-mortem on Mr Cheema, who is described as hard working and well-liked, was inconclusive and police are currently awaiting the results of further toxicology tests to establish exactly which poison he and his fiance may have consumed.
A 39-year-old Southall woman has been charged and is waiting to stand trial in May for murder and attempted murder.
A 54-year-old Windsor man was also arrested in connection with the investigation and has been bailed to appear at a west London police station in March pending further enquiries.
Anyone with information is asked to contact the Met's Incident Room on 0208 247 7821 or contact Crimestoppers, anonymously, on 0800 555 111.