Roads and Transport Policing Command officers are appealing for witnesses and information after a fail to stop collision in Paddington left a motorcycle rider with serious head injuries.
On Thursday, 5 January police were called by London Ambulance Service (LAS) at around 1940hrs to the collision on Edgware Road, near the junction with Newcastle Place, W2.
Officer attended and the rider of a Piaggio Vespa scooter - a man aged 21 - was taken by LAS to hospital. He is described as being in a critical condition.
The vehicle the scooter had been collision with did not stop at the scene.
At this early stage of the investigation officers believe the other vehicle involved was a white or light coloured, transit-style van.
Detectives from the Serious Collision Investigation Unit are carrying out enquiries into the circumstances of the incident.
They are appealing for any witnesses to the incident, or anyone with any information about the van involved, to contact them.
Anyone that can assist the investigation is urged to call the witness lines on 020 8543 1557. Alternatively police can be called via 101 or tweeted @MetCC.
To give information anonymously contact Crimestoppers on 0800 555 111 or visit crimestoppers-uk.org.