James Middleton is a keen animal lover, and has previously spoken about how his therapy dog, Ella, helped get him through some of his worst times as he battled depression.
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And on Tuesday, the businessman revealed how "honoured" he felt to write the foreword to Leo & Friends: The Dogs with a Healing Touch, which explores how a therapy dog helped author Lyndsey Uglow.
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James uploaded two photos, one of a dog holding the book in its mouth, and another of the first time that he met Lyndsey at the Kennel Club's Friends for Life competition in 2020.
In his caption, the 34-year-old wrote: "I believe that dogs teach us our worth in the love they give so freely and unconditionally.
"No wonder that, however long they are with us - for life, a visit, a moment at a hospital bedside - they leave behind a beautiful, indelible paw print on our hearts."
He added that he was "honoured" to have been asked to write the book's foreword and praised Lyndsey for her "pioneering work".
James was full of praise for Lyndsey
James explained that she "represent[s] everything there is to say about the powerful healing bond that exits between dogs and children."
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He added: "In my experience dogs can be a powerful intervention in our lives, as the patients' stories in this wonderful book prove without shadow of doubt."
Kate's brother was inundated with support from his followers, as one said: "How wonderful.. I truly believe in the power of a dog's unconditional love for a lifetime or even for a moment."
Leo & Friends: The Dogs with a Healing Touch by Lyndsey Uglow, £11.38, Amazon
Many others posted strings of heart and applause emojis, while some made use of the pawprint emoji.
Lyndsey has used a therapy dog to help alleviate her own mental health as her son battled leukaemia, and through her work has made it possible for over 10,000 children, many critically ill, to receive a visit from a therapy dog.
Ella has helped James during his battle with depression
James has been very open with his mental health battles, having been diagnosed with clinical depression, and to mark Mental Health Awareness Week back in May he detailed his initial reaction to his diagnosis.
"It has been exactly 1255 days since I got diagnosed with clinical depression - but that day was the first day I learnt about mental health and how it is integral to the way we live our lives," he said.
He continued: "Ten days later I disappeared, I packed my dogs into my car and, telling no one where I was going, drove to a wild and remote part of the Lake District. There I swam in an icy lake, took solitary walks on snow-capped mountains and stayed alone in a remote cottage, trying to still the tumult in my mind.
"Why did I do this? I wanted to be in Nature. Nature is central to our psychological and emotional health."
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