The 37-year-old man walked from Maiden Lane along a footpath in Ewhurst Wood, near to Crawley Avenue, around 5pm on Friday (October 30).
One of the suspects is described as black, tall, of wide build and with hair plaited in a hexagonal design. He was wearing a surgical mask and a Canada Goose puffer jacket with brown fur around the hood.
The two other suspects are both described as Asian with one wearing a mask with a shark tooth design, and the other wearing an Adidas branded face mask.
Anyone who saw what happened, or who saw any suspicious behaviour in the area at the time, is asked to contact police online or by calling 101 quoting serial 1129 of 30/10.
Alternatively, you can contact the independent charity Crimestoppers anonymously on 0800 555 111.