New CCTV footage shows Lee Peacock, 49, at North Wembley Station on the evening of August 19.
Police have released the footage in the hope the public may be able to help officers to locate him.
Detectives want to speak with Peacock following the deaths of two people last week.
At around 21:30pm on Thursday night, August 19, 45-year-old Sharon Pickles was found dead at a residential address in Ashbridge Street in Marylebone.
A few hours later, at about 2.15am on Friday, August 20, the body of a 59-year-old Clinton Ashmore was found at a property in Jerome Crescent.
Both victims died from knife injuries. Police believe Peacock knew both victims.
❓ Have you seen this man? ❓
Detectives have released CCTV footage of Lee Peacock to assist the public in helping locate him.
DSU Luke Marks: "Anybody who sees him, call police immediately on 999. I urge members of the public not to approach him."https://t.co/DJkz7dzPXz pic.twitter.com/yVdgEVzGnG
— Metropolitan Police (@metpoliceuk) August 23, 2021
Detective Superintendent Luke Marks, of the Specialist Crime Command, said: “I am appealing today for further information about the whereabouts of 49-year-old Lee Peacock, who we need to speak to urgently about the murders of two people in Westminster.
“I am asking anybody who sees Lee to call us immediately on 999. I would urge members of the public not to approach him, but instead to call police as soon as possible.
“I believe Lee could have important information about the deaths of two people whose bodies were found at two properties in Westminster on the 19 and 20 of August.”
DSU Marks continued: “At this early stage we are retaining an open mind concerning motive, but we are treating these crimes as linked.
“I know this will cause concern among the community but I would like to reassure the public that we have a dedicated team of officers who are tasked with finding Lee.
“And once again I would like to appeal for anyone who sees him to call 999.
“We are also offering a £20,000 reward for any information leading to the conviction of the individual responsible for these murders.”
For an immediate sighting of Lee Peacock, please dial 999.If you have information about his whereabouts call police on 101 or contact Crimestoppers anonymously on 0800 555 111.