A man has died after being arrested by London police on Thursday night.

London police say they were called to the area of Wonderland Road South and Exeter Road after reports of an impaired driver.

A vehicle and driver were found in the south ditch of Harry White Drive at Wonderland Road, on the southern outskirts of the city.

The driver was arrested and taken to police headquarters. While in the cell bay area, the man allegedly became unresponsive in the back of a police cruiser. An officer conducted CPR until paramedics arrived, police said.

The man was taken to hospital, where he was pronounced dead.

The Special Investigations Unit has been called in to investigate. The watchdog probes incidents that involve harm or death during interactions with police.