A man was stabbed in a "unprovoked attack" when cycling to shops in Greenford at the weekend.
The 33-year-old victim was riding from the Rise towards Sudbury Hill Tube at about 7.30pm on Saturday (March 28) when three men pushed him off his bike and assaulted him as he entered Ridding Lane.
Police said the victim suffered five stab wounds to his legs, chest, armpit and back.
Not realising the severity of his injuries, the victim got back on his bike but collapsed shortly afterwards, police added.
The victim was taken by the London Ambulance Service to a central London hospital where he remains in a stable condition.
Detective Constable Steven Constable, from Acton CID, said: "This appears at this stage to be an entirely unprovoked attack on a man who was merely cycling to the shops. Nothing was stolen during the assault.
"We are appealing for any witnesses or anyone with information about the suspects to contact us as soon as possible. It may be someone saw them hanging around the area in the minutes or hours leading up to the attack."
The first suspect is described as black, around 25 years old, about 6ft and slim.
He wore dark clothing and is thought to be local to the area.
The other suspects were also black and aged about 21 or 22. They were skinny and wore dark clothing with their hoods up.
Anyone with information is asked to contact Acton CID on 020 8721 7029 or if you wish to remain anonymous, Crimestoppers on 0800 555 111.