The incident occurred at around 7.55pm on Thursday, August 24, in the woods close to Rants Meadow where the victim was walking.
They were approached by an off-the-lead greyhound style breed dog, who bit him on the hand, causing an injury which required hospital treatment.
The owner was believed to be apologetic for the dog’s behaviour and tried to get it onto the lead.
“Our enquiries are continuing, and we are appealing for anyone with information to please come forward,” said PC James Stockwell, from the Dacorum Safer Neighbourhood Team.
“We are appealing to speak to the owner of the dog who is described as a white woman in her 60’s with short grey hair.
“Anyone with information is asked to email me at firstname.lastname@example.org.”
Alternatively, contact Crimestoppers anonymously on 0800 555 111 or online at crimestoppers-uk.org.