A man has been arrested on suspicion of driving while unfit through drugs over a collision in west London in which a young child was killed, the Metropolitan Police said.

Officers were called to Eastcote Road in Ruislip just after 4pm on Sunday to reports of a collision involving a car and three pedestrians, including a 22-month-old child in a pushchair.

The Met said officers, including some who were off duty, and the London Ambulance Service attended but despite their efforts the child was pronounced dead at the scene.

Another pedestrian, a man in his 30s, was also taken to hospital and remains in critical condition.

The force said a man aged in his 40s was arrested on suspicion of causing death by dangerous driving, causing serious injury while driving, and driving while unfit through drugs.

The child’s next of kin have been informed and are being supported by specially trained officers.

Detectives from the Met’s Serious Collision Investigation Unit are investigating and are appealing for witnesses or anyone with dashcam or CCTV footage to come forward.

Detective Sergeant Sarah Donegan said: “Our thoughts are with the child’s parents at what must be an unimaginably difficult time.

“We have launched an investigation to establish the circumstances of what happened and I am asking anyone who was in the vicinity at that time who may have seen something, or has dashcam footage or CCTV, to come forward and help us with our investigation.”