A passenger in a car in North Kensington is in a serious but stable condition after being stabbed.
The incident happened at St Helens Gardens near Ladbroke Grove just before midnight on Tueaday (April 19).
Officers from Trident and Area Crime Command, which tackles gang violence, are investigating.
Metropolitan Police and ambulance crew were called to the scene at 11.48pm and found a 21-year-old with stab injuries. He was taken to a central London hospital where he still remains.
The victim is thought to have been sitting in the back of a car at the time of the assault.
The attack happened only hours before a similar one took place in nearby Harrow Road, where a driver with stab wounds was found in his car that was crashed into a lamp post.
Police have arrested a man in connection with the incident who is being questioned, but are asking anyone with information to come forward and assist with their inquiries.
Call police on 101 or Crimestoppers anonymously on 0800 555111.
St Helens Gardens is the same road on which drug dealer Bill Mendes assaulted and robbed a woman. He was jailed before Christmas .