The collision happened on Fakenham Road along the A1067 near Sparhamhill, near to the junction of Nowhere Lane at 11.15 am.
 
It involved a red Polo, a green Volvo, a blue Nissan Almera and a white Peugeot Bipper van.
 
The driver of the Polo, a woman in her 50s, suffered serious injuries as a result of the incident. She remains in hospital in a serious but stable condition.
 
The other drivers involved suffered minor injuries as a result of the incident.
 
Officers are appealing for anyone who may have witnessed the collision, or has any information about the manner of driving of the Polo along the A1067 between Norwich and Lenwade prior to the collision, to come forward.
 
Anyone with information should contact PC Mike Stolworthy in the Acle Roads and Armed Policing Team via email or call 101 quoting incident NC-28012022-127.
 
Alternatively contact Crimestoppers anonymously on 0800 555111.