Police are appealing for witnesses to a collision that occurred yesterday on the southbound carriageway of the M40 between junctions five and four.

At about 3.05pm a white Renault Kangoo with five occupants collided with the central reservation, causing it to roll over.

A four-year-old boy was taken to the John Radcliffe Hospital, Oxford, by air ambulance suffering from serious injuries. He remains in hospital in a serious condition.

The driver, a 30-year-old man, was taken to the John Radcliffe by ambulance suffering from serious injuries.

A woman and two other children were taken to Wexham Park Hospital with minor injuries and were later discharged.

The southbound carriageway of the motorway was closed for about four hours. The delays in reopening the carriageway were caused by vehicles breaking down in the tailbacks.

PC Liz Johnson said: “It is believed that no other vehicles were involved in this collision. I would like to hear from anyone that may have seen the vehicle prior to the collision or who witnessed the collision itself.”

Anyone with any information is asked to contact PC Liz Johnson at Amersham Roads Policing base via 0845 8 505 505. If you don’t want to talk to police or leave your name, please contact the Crimestoppers charity on 0800 555 111.