Old and increasingly unwell, Walnut's owner Mark Woods decided he needed to be put out of his misery.
But before going to the vet to have his beloved whippet put down Woods took him to his favourite Cornish beach for one last walk.
And he accompanied hundreds of well-wishers along to say goodbye to Walnut.
Wrapped in a blanket Walnut was carried by Woods along Porth Beach on Saturday (UK time), while dozens of other dogs brought by their owners yelped alongside.
It was a special moment for Woods, who said he had taken the decision to have Walnut put down after realising the 18-year-old was "on his last legs".
Woods, from Newquay, has three other whippets but said Walnut "has got something about him" and they've been through an "awful lot together".
He had earlier put out a call on social media for anyone who wanted to accompany him and Walnut on their last walk together to join them at Porth Beach.
Woods said he had been "flabbergasted" by the response to his call for people to join him and Walnut.
When Woods reached the water's edge he gently lowered Walnut onto the sand, allowing him to dip his paw in the water.
Speaking before taking Walnut to the vet Mr Woods said: "I didn't want to just sit here moping around, I thought we should go for a last walk so his day was reasonably normal, and mine was reasonably normal as well.
"I thought it would be nice to walk with others and share the day, I always walk on my own and it gets boring on my own so I thought it would be nice.
"He has always travelled around with me, all around London and he stood by the swimming pool whilst I gave diving lessons, we've been in all sorts of bizarre situations together, various girlfriends who have got upset because I always put him before them, I have always put him first and maybe I shouldn't have but he is just such a special dog.
"I got as message from a guy who really put his finger on it, he said how dogs really bring the best out in people, and then people do the best things."
Then, after their last stroll as man and dog, it was time to say goodbye.
Woods later confirmed that Walnut had died at 11.56am.
He said: "The family and our three whippets Monty, Nelson and Charlie were also in the room.
"He went very quickly and in my arms. I am writing this post because I owe it to everyone who has supported myself, my family and most importantly Walnut.
"Thank you to the hundreds of people that attended this walk this morning and to all those that had their own walks with their beloved pets at 9.30am all around the world.
"I also want to thank the wonderful people of Newquay for their support which I will never forget as long as I live. God bless you all."