Detectives are asking those with dash cam footage to come forward following a fatal collision in Carshalton.
Police were called at 11.15pm on Wednesday, 6 August to Wrythe Lane, Carshalton, following reports of a road traffic collision involving a van and a motorcycle.
Officers attended with LAS.
The rider of the motorcycle, a 24-year-old man, was taken to hospital, where he later died. His family have been informed.
The driver of the van, believed to be aged in his 30s, was arrested on suspicion of drink driving and causing death by dangerous driving. He remains in custody.
Enquiries continue, led by the Serious Collision Investigation Unit.
Any witnesses, or those with dash cam footage, are asked to call the Serious Collision Investigation Unit on 0208 543 5157, or 101 ref CAD 8634/05AUG.