Police have released CCTV images of a man brandishing a knife minutes before a victim in his 50s was stabbed in the stomach in a motiveless attack.

Footage shows a suspect waving the weapon around at a bus stop on the Brunel Estate in Westbourne Park, west London, at around 5.15am on Wednesday April 22.

Around 20 minutes later, emergency crews were called to treat a man who had got on to a bus asking for help. He remains in a critical condition in hospital.

Police believe he was attacked around 100 yards from where the suspected attacker was filmed with the knife.

Detective Chief Inspector Christina Jessah, of the Metropolitan Police, said: “We still really need to identify the man pictured and would urge anyone with information to contact us immediately.

“At this stage we don’t know why the victim was stabbed and there is no obvious reason. But it was undoubtedly an awful attack and he remains in hospital fighting for his life.

“We’d still like to speak to anyone who was using an N28 or N31 bus in the area of Westbourne Park Road around the time of the incident who may have seen a man acting suspiciously, or possibly local residents who may have heard raised voices – no matter how insignificant it may seem, please do give us a call.”

Anyone with information can call police on 101 quoting 999/22APR, tweet @MetCC or to remain anonymous call Crimestoppers on 0800 555 111.