A new five-figure reward has been offered in an attempt to find one of Britain's most wanted fugitives.
Shane O'Brien, 28, is the chief suspect in the violent murder of 21-year-old Josh Hanson, who was stabbed to death in an unprovoked attack in west London last year.
It is believed O'Brien has fled to several countries, and may now be in the United Arab Emirates, possibly travelling on a fake passport.
An initial reward of £10,000 for information leading to his arrest and conviction has been doubled, the Metropolitan Police said.
Detective Chief Inspector Noel McHugh, from the Met's homicide and major crime command, said: "We hope the offer of this substantial reward will encourage anyone with information to come forward and help us detain O'Brien.
"Clearly O'Brien is being helped by other people to evade police - some of those allegedly assisting him have already been arrested.
"The fact that O'Brien is moving from country to country demonstrates he has the means to travel without using his own identity.
"So we would ask people to look closely at O'Brien's photo and if you recognise him contact us.
"While our information links O'Brien to Dubai, we have taken calls about potential sightings across the world which have all been followed up.
"We really need the public's help. If you have information don't assume it's something we already know, you could hold that crucial clue."
Police said the suspect, added to the National Crime Agency's most wanted list in March, has a distinctive tattoo on his back that reads "Shannon 15-04-06".
Originally from Ladbroke Grove, he is described as white, 6ft tall with grey eyes and short dark brown hair. He may use the name Troy O'Brien.
Mr Hanson, from Kingsbury in north-west London, died after a stabbing at the RE Bar in Hillingdon at about 1.10am on October 11 last year.
He was found with a serious wound to the neck and was pronounced dead at the scene.
A post-mortem examination gave cause of death as haemorrhage, inhalation of blood and an incised wound to the neck.
His mother Tracey Hanson said: "It has been eight and a half months since my son and Brooke's brother Josh was murdered in an unprovoked knife attack and we are still fighting for justice.
"Not a single second, minute or hour of the day goes by without us not being able to properly grieve or mourn for Josh as Shane O'Brien, the man police would like to speak to in connection with Josh's murder, is still at large.
"We are asking the public to help in any way they can. If you have the slightest doubt in your mind as to whether you think you may have seen Shane O'Brien or know someone who has, please come forward and help us get justice."
Anyone with information is asked to contact police immediately.