Police believe a number of people were in the area when a man in his 20s was seriously assaulted.
Officers were called to the Old Cattle Market car park in King's Lynn at 4.28am on Saturday, October 12, to reports a man had been assaulted.
On arrival they found a man with serious head injuries. He was taken to Addenbrookes Hospital where he remains in a stable condition.
Detectives believe a number of people were in the area at the time of the incident and are re-appealing for anyone who may have witnessed the assault to contact them.
A 23-year-old man who was arrested in connection with the incident remains under investigation whilst the enquiry continues.
Anyone who saw the assault, or anyone with information, should contact Det Con Claire Twite at King's Lynn CID on 101.
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