A toddler in a pushchair has died after being hit by a car in north-west London, during an incident which also left a man in his thirties critically injured.
The Metropolitan Police have arrested a 40-year-old man on suspicion of causing death by dangerous driving. He is also suspected of driving while unfit due to drug use. The suspect is currently in custody.
Police rushed 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 police 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.
The relatives of the child have been informed and are being supported by specially trained officers, the force said.
Detectives from the Met's Serious Collision Investigation Unit are investigating and are appealing for witnesses or anyone with dash-cam or CCTV footage to come forward.
Det Sgt 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 dash-cam footage or CCTV, to come forward and help us with our investigation."
Witnesses were asked to call 020 8246 9820, or the independent charity Crimestoppers on 0800 555 111.
Additional reporting by the agencies