A man has been arrested on suspicion of drug driving after a crash that left another man in hospital with serious injuries.

Police say they received a report of a collision involving a pedestrian and a white Mercedes in Exchange Road, Watford, shortly before 11pm yesterday (Friday, June 24).

Police closed Exchange Road and directed motorists to avoid the area.

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The pedestrian, who is an adult male, suffered a serious head injury and was taken to Watford General Hospital by ambulance services during the night.

A police spokesperson said he is still currently in hospital in a stable condition.

A 36-year-old man has been arrested on suspicion of a drug driving offence and released while an investigation continues.

Police are asking anyone who saw what happened to call the non-emergency number 101, quoting reference ISR 918 of 24 June.