The assault happened between 7.30pm and 8pm on Wednesday, August 24 when the victim was sat in his car in the Gossmore Recreation Ground car park, in Gossmore Lane.
He was approached by a man, described as black, with short hair, aged between 30 and 35, of muscular build, over 6ft 4ins tall and wearing a black t-shirt, who held a small knife to his throat through his open car window.
He was then punched twice by the man, who left in a 2007 plate black Volkswagen Golf GTI.
The victim required hospital treatment but has since been discharged.
Investigating officer PC Rob Allen said: “We are appealing for anyone who may have seen this assault which left the victim requiring extensive treatment.
“If you saw this incident or shortly after saw a Black VW GTI Golf with 2007 number plate making off on Gossmore Lane, right onto Lock Road and afterwards we would like to speak to you."
Contact police on 101 or Crimestoppers anonymously on 0800 555111 with information.
Top Ten Articles
The Met Office has issued a yellow alert for Windsor and Maidenhead, Slough and Wokingham, warning that rain moving eastwards across the south of the country may turn to snow in some places.