He was so closed off from the world, he refused to step foot outside his kennel.
But after spending time at the RSPCA, he has "blossomed" into a loving dog who enjoys playing with toys and walking in familiar places.
Rupert, a Staffordshire bull terrier, has spent more than 500 days at the RSPCA's Brighton Animal Centre after being brought over from another animal rescue.
The three-year-old dog is still searching for a "very special home" with owners who "will allow him to take things at his own pace".
A statement reads: "Rupert came to us in February 2021 via another rescue and instantly broke all of our hearts.
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"We had never met such a shut down dog who feared human contact to such an extent.
"It took a long time for him to accept any affection and weeks for him to venture into the outside world.
"Through patience, dedication and a lot of love Rupert has now blossomed.
"Due to his past experience, he is still extremely anxious and nervous of new situations and probably always will be."
Rupert needs an owner with bull breed and nervous dog experience who can commit their time to his continued rehabilitation.
He must live in an adult-only home with no visiting children, cats or small animals as he would chase them.
His new owner will need to commit to shelter visits over a period of weeks before his adoption and will need to continue to work with the RSPCA after taking him home.
"Rupert is still very nervous and fearful when meeting new people and it takes a few meetings before he is happy to accept treats from them," the statement adds.
"He loves other dogs and is happy to play with dogs of any size and sex. He knows sit and his name on command and loves food and treats."
The RSPCA is urging people to turn to adoption centres rather than breeders when wanting to welcome a new pet into their home.
"While it may be easy to find animals on the internet or even spend hundreds on an expensive breeder, you could risk heartache or huge vet's bills if you don't do your homework," a statement reads.
"By adopting and not shopping you'll also feel good for doing good - by giving an animal a second chance at life in a loving home!
"Plus, adopting from us means that you can relax knowing that all our animals are healthy, neutered, vaccinated and microchipped.
"As with all the animals we rehome, we'll pass on the details of their behaviour and veterinary treatment. You'll likely know more about your rescue animal's history than if you were to buy an animal online!
"We've taken the time to get to know each animal as an individual, to understand their likes and dislikes and to prepare them for life in a loving family, which means there are less likely to be nasty surprises when you get home!
"When you adopt a cat or a dog from one of our centres, you'll also get four weeks free pet insurance, which is vital to protect your pet's future as well as your bank balance! There's so much to gain from rescuing an animal in need."
If you're interested in rehoming Rupert, or any other dogs at the RSPCA's Brighton Animal Centre, contact their team via email on info@rspcabrighton.org.uk.
Their main centre and reptile unit is open from 10.30am to 4pm Tuesday to Sunday - with adoptions by appointment only.
Do you have a dog story to share? Email paige.freshwater@reachplc.com.
