A passenger fell from a van as it travelled southbound between junction 9 for Redbourn and junction 8 for Hemel Hempstead on the M1 in an unexplained incident last night.

Herts Police are appealing for witnesses and information following the accident when a man fell from a white Volkswagen panel van before 6.40pm yesterday evening.

The driver, a 43-year-old man from Hayes, stopped the vehicle and the man, a 44-year-old from Harrow, was taken by air ambulance to Addenbrookes hospital with serious head injuries.

He remains in a serious but stable condition.

Anyone with information is asked to contact Herts Police on non-emergency number 101.