This incident happened at around 12.40pm on Monday 15 February 2021 in the car park at the rear of Sainsburys Local supermarket in the High Street.
It is alleged a man in his 40s was assaulted by two other men before losing consciousness.
He received medical attention at the scene from South East Coast Ambulance Service and was taken to a local hospital for treatment to a head injury.
Investigating officer PC Carl Johnson said: ‘The car park was busy at the time of the incident and we are appealing for witnesses to contact the appeal line.
‘We are also asking any motorists with dascam who were in the area at the time and residents with doorbell cameras to check for footage that may assist the investigation.’
Anybody with information is urged to call 01622 604100, quoting reference 46/25499/21.