Detectives from the Metropolitan Police are appealing for information over a London murder.
Shane O'Brien, 27, of Ladbroke Grove, is being sought by officers who need to urgently speak to him.
A £10,000 reward is now available for information leading to O'Brien's arrest and prosecution.
Officers say although he has links to the Ruislip area, he could be anywhere in the country.
Detective Chief Inspector Noel McHugh, of the Homicide and Major Crime Command, 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 O'Brien to contact us, or ask that anyone who has seen him or who knows where he is to contact us as well. I do believe someone out there will know where he is.
A substantial reward is now on offer to anyone with information that leads to O'Brien's arrest and prosecution and we hope this will encourage someone to come forward."
Shane is described as a white man, 6ft and of muscular build. He should not be approached by members of the public. Any sightings of him should be reported to police immediately on 999.
Anyone with information about his whereabouts can call the incident room on 020 8785 8099 or contact Crimestoppers anonymously on 0800 555 111 or via crimestoppers-uk.org.
Mr Hanson, 21, of Kingsbury died after an incident at the RE Bar in Field End Road, Eastcote, Hillingdon, at approximately 1.10am on Sunday, October 11.
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).
DCI McHugh added: "We have had a positive response to our appeal but are still asking 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."
"We have had a very positive flow of information from members of the public following our appeal for which we are grateful."
"We are responding to all this information."
Speaking previously about Josh DCI McHugh 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."
Any witnesses or anyone with information should also call the incident room or Crimestoppers.
There have been no arrests at present and enquiries continue.
A post-mortem examination at Uxbridge mortuary on Tuesday, 13 October gave cause of death as haemorrhage, inhalation of blood and an incised wound to the neck.