A father and daughter remain in a serious condition in hospital following a three-vehicle crash on the M1 yesterday.

Police are appealing for witnesses to the collision between a lorry and two cars at junction 6 in the northbound carriageway at around 9.40am.

Investigating officers said at least 20 people stopped at the scene and helped right the cars, a white Nissan Juke and a blue Toyota Aygo, which where overturned in the crash. The lorry was also flipped on its side in the collision.

The driver of the Toyota, a 58-year-old man, suffered serious injuries as did his 22-year-old daughter. They were both taken to St Mary’s hospital in London with serious injuries and remain in a serious condition at this time.

The lorry driver, a man in his 30s, did not need hospital treatment. The driver of the Nissan, a woman in her 30s, suffered slight injuries and was taken to Watford General Hospital.

The road was closed between junction 5 and junction 6 for around six hours while investigations took place.

PC Boris Kahn said: “I am aware that at least 20 people may have stopped at the scene to help in turning the cars back onto their wheels as they had overturned.

“Officers were not able to speak with all these people before they left the scene and I would appeal to these people to please contact me with information.

"I would also like to thank them for their assistance at the scene as their actions are believed to have prevented further significant injuries to the father and daughter.

“I would also be keen to hear from anyone else who can assist with my inquiries as to the cause of the collision.”

Anyone with information should please contact PC Kahn via the Herts Police non-emergency number 101.