A man suffered cuts to his face after confronting a 20-year old man who was seen to be vandalising a bicycle in Newbury on Tuesday.
The 36-year old victim was pushed to the ground and was cut above his left eye when he attempted to intervene.
He was treated at Basingstoke Hospital and has since been discharged.
The offender is described by police as white, aged about 20, 5ft 9ins, with mousey-coloured hair, and was wearing a white T-shirt and dark trousers.
The incident took place at around 9.50pm on Tuesday in Market Street.
Thames Valley Police are now appealing for witnesses and anyone with information should contact investigating officer Sian Betteridge from Newbury local CID via 101 or anonymously to Crimestoppers on 0800 555 111.