Police have released a description of a man they would like to speak to for information over the murder of 21-year-old Josh Hanson.
Detectives are now treating the search for suspect Shane O'Brien, 27, of Ladbroke Grove, as a "national manhunt" and believe he could be "anywhere in the UK".
A manhunt is an extensive and thorough search for a wanted suspect or criminal, police explained.
Shane O'Brien is described as a white male, 6ft tall, and of muscular build.
The Met said he should not be approached by members of the public.
He has links to the Ruislip area but police believe he could be anywhere in the country. Any sightings of him should be reported to police immediately on 999.
Mr Hanson, of Kingsbury, Brent, died after an incident at The Re Bar in Field End Road, Eastcote, Hillingdon, at around 1.10am on Sunday (October 11).
Police officers and London Ambulance Service attended and Mr Hanson was found suffering a serious wound to the neck. He was pronounced dead at the scene.
A murder investigation was launched by Met's Homicide and Major Crime Command (HMCC).
Days after his death, Josh Hanson's mother pleaded for help to find her son's killer.
Detective Chief Inspector Noel McHugh, who is leading the investigation for the HMCC, said: "We are very keen to speak to Shane O'Brien as part of our ongoing enquiries and we believe he could be anywhere in the UK.
“I would appeal directly to Shane to contact us, or ask that anyone who has seen him or who knows where he is to contact us as well.
"We have had a positive response to our appeal but are still appealing to anyone who was in the RE bar between midnight and the time of the incident and has not yet contacted us to get in touch."
DCI McHugh previously said: "Josh was a hard-working young lad, up at 5am for his job as a roads planner and often working seven days a week.
“He had everything to live for and when he went out that Saturday night, no one could have imagined what would happen to him. His family is in pieces."
This week, Hillingdon borough commander DCS Nick Downing moved to assure local people Mr Hanson's death was not gang-related.
Anyone who knows of Shane's whereabouts can call the incident room on 020 8785 8099 or contact Crimestoppers anonymously on 0800 555 111 or via crimestoppers-uk.org.
