A man who was admitted to hospital two weeks after being assaulted has died.
The 47-year-old was attacked at 23:00 GMT on 2 December near Creams restaurant in Western Road, Brighton.
It was reported the next day but Sussex Police said the victim did not seek medical treatment at that time.
He was later admitted to hospital on 17 December after becoming seriously ill. Police said a manslaughter investigation was now under way and appealed for witnesses to contact them.
Officers would like to hear from anyone who saw the assault or the victim between 2 to 17 December.
A spokesperson for the force said an investigation had begun into how the man died, what events led up to his death, and whether any injuries suffered in the assault caused his death.