Thames Valley Police is appealing for witnesses to an assault in Reading.
The incident happened on Tuesday 4 September but was only reported to the Force on Sunday 4 November.
The victim, a man in his forties, was walking through Palmer Park playing field at around 10pm when he was approached by four offenders who assaulted the man.
The victim was immediately knocked unconscious and it is thought something similar to a knuckle duster may have been used. He regained consciousness at around 5am on the following day, Wednesday 5 September, and was on the A3290, about two miles from Palmer Park.
He suffered lacerations to his face, an eye injury and swelling on his head but he did not require hospital treatment.
Investigating officer PC Josh Gillespie of the Reading Investigation Hub, said: “This was a vicious attack which left the victim confused and injured.
“I would appeal for anyone with information to come forward and make a report, even if you think it may be insignificant.
“To make a report you can call the Thames Valley Police non-emergency number on 101, quoting the reference 43180338320 or you can make a report online.
“If you do not want to speak to police, please call the independent charity Crimestoppers anonymously on 0800 555 111”.