The red and white-coloured Staffordshire bull terrier was found wandering in Cowley Recreation Ground on March 11 with no tags and no microchip.
He was passed on to police and many members of the public tried to find his owner before he was put down - it was believed he was a cross with a banned Pitbull type dog.
The case was picked up by specialist dog law firm Parry Welch Lacey (PWL) who warned last week that the dog would be put down unless his owner was found.
Jess Lamb, a paralegal with the firm, told getwestlondon : “The dog has been put to sleep unfortunately.
“A few weeks ago a woman contacted us because she'd seen this dog loose.
“We contacted the police.
“Unless we found the owner then no one else could come forward to take the dog.”
A social media campaign to found the dogs owner prompted the hashtag #Hillingdonboy but on Thursday (April 6) PWL said it had not yet heard from the dog's owner.
Ms Lamb confirmed to getwestlondon on Monday (April 10) that the dog had been put down over the weekend.
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