He was discovered by members of the public in an alleyway opposite The White Hart Pub on the High Street, Just after 2.20am on Saturday morning 14th.
The victim was taken in an ambulance to Watford General Hospital, where he's been placed into an induced coma.
His family have been informed and they are being supported by officers.
Detective Inspector Tom Leeks, who is investigating, said: “We believe the victim’s injuries are consistent with being beaten and I want to reassure the community that we are doing all we can to find the person or persons responsible for this crime.
“Were you in the Old Town area yesterday evening, or the early hours of this morning? Did you see or hear anything suspicious, or did you witness anyone leaving the area in a hurry?
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