An elderly woman is in a "critical but stable condition" following a collision with a car in a supermarket car-park.

Police said the woman, who is in her eighties, was taken to Watford General Hospital after the incident involving a green Volvo in the Tesco car-park, Harefield Road, Rickmansworth, at 5.33pm on Monday.

Hertfordshire Constabulary said the green Volvo 940 was reversing when it collided with the 82-year-old woman who was putting her shopping in the boot of her car.

She was later transferred to the Royal Free Hospital in Hampstead, London, officers said.

A 68-year-old man was arrested on Monday evening on suspicion of failing to stop at the scene of a collision.

PC Bob Hauxwell is investigating and said: “I would appeal to anyone who was in the area at this time and saw what happened or anyone who has any information which would assist the investigation to please contact me via the Herts Police non-emergency number 101.”

He has been released while officers carry out further enquiries.

Officers have asked anyone who witnessed the incident, and has not spoken to detectives, to contact police via 101.