The House is overwhelmed by artwork. It’s piled up on drawers, spilling out of cupboards, teetering on shelves. Some is finished, some half-worked up, other pieces are no more than an inked line suggesting a shape. And everywhere, the same motifs: horses, moles, foxes and a tow-haired boy. Several of the drawings, spotted with tea and marked with dust, have spilled onto the floor of the South London Victorian terrace where a small and ancient dog snuffles at their crinkled edges.

Amid this fantastic mess stands Charlie Mackesy or, as he introduces himself, “a random scruffy artist, who happens to have made a little book”. He might be employing understatement. The random scruffy artist has previously collaborated with Nelson Mandela and his little book is an international phenomenon.

With its origins in a series of social media postings that went viral, The Boy, the Mole, the Fox and the Horse is a picture book about a young boy who encounters three animals and, with them, learns the wisdom of kindness. The book was published in October 2019, just before the pandemic arrived. “No one knew of course,” he says, “but I do remember thinking there was something coming and that we had to get the book done. I felt the weight of all that fear and loneliness and loss.”

Without knowing or planning it, Mackesy had written a psychological survival handbook for a worldwide epidemic. By December 2021 there were more than 5.5 million copies in print internationally. In the UK alone it had sold 1,967,949 copies by last Christmas, becoming the best-selling UK hardback since records began. “I didn’t imagine we’d be selling very many books,” says Mackesy. “Certainly not that many.”

With his ink-spotted workman’s shirt and shock of gray curls, he doesn’t look like the wealthy man such sales must be making him – a question Mackesy, Radley-educated scion of a military family, sidesteps gently. “If you want to be a millionaire, you don’t do this job,” he says. “It’s got to be your vocation, something in you. And for me, I like making people feel a bit better about life.”

Now The Boy, the Mole, the Fox and the Horse, a Winnie-the-Pooh for our demanding times without, perhaps, Pooh’s steely core, is coming to BBC One this Christmas. Co-directed by Mackesy and Peter Baynton, its soundtrack composed by Isobel Waller-Bridge and performed by the BBC Concert Orchestra, it’s a delightful 30-minute animation set in a winter landscape modeled on the Northumberland of Mackesy’s youth.

Here, when the flurries of snow settle, a mole takes up with a lost boy and the two travelers are joined by a fox and a horse. “They all discover in their own way that they’re lost,” says Mackesy. “All four of them need connection, need shared vulnerability, and their home is in those relationships.”

“I didn’t imagine we’d be selling very many books.”

Mackesy is finely attuned to such things, to questions of being an outsider in a world that can seem cruel or uncaring. Nearing 60, Mackesy first went into therapy when he was 30. “There was a time when I’d lost a good friend and I was finding living day-to-day difficult. You don’t think asking for help is an option, you don’t think it’s going to achieve anything and you think you’re being indulgent, so you just have another piece of cake and keep going. It is the English way, but there comes a time when that’s not enough.

“I remember my first session,” he says. “It was huge to me because all my life, I thought: you’re a freak, or you’re weird, or you’re abnormal. But what I got back that day was, ‘You and the rest of the world!’ That, to me, was like walking through a door into a new world of hope and possibility. My humanness, in all its oddness, was accepted and universal. I realized, to be human is to be like each other.”

This sense of shared humanity means he likes working in a team and relished guiding the 150 animators it took, from countries around the world, to turn the book into a film. “Each frame is hand-drawn,” says Mackesy. “I went through with them frame after frame. I was like a teacher. I’d say, ‘Make this line thicker under the tummy,’ then send it on to them. Suddenly they started doing way better drawings than I could. I remember when we got the boy’s face right. It was June 2021 and I ran around the room, screaming. It was a massive moment.”

The soft center of Mackesy’s philosophy is best illustrated in an exchange between the horse and the boy. The horse asks, “What do you want to be when you grow up?” “Kind,” says the boy. Understandably, this had a strong resonance during the pandemic when thousands of people, often in lockdown or working in hospitals, depended on the kindness of others.

“People were climbing the walls,” says Mackesy. “I would do a post [on Instagram] and it would get 150,000 likes and a lot of comments. People said, ‘This is keeping me going.’ Nurses told me that my work was on display in wards. I had e-mails from hospitals across the world.”

Given his own fragility, was Mackesy ever overwhelmed by this tide of feeling from people in traumatic and tragic circumstances? He has, after all, his own burdens to carry. When not in London, where he lives alone, Mackesy is in Suffolk, where his sister looks after their elderly mother who suffers from dementia. “There were moments where I did feel this is too much – the weight of people’s emotion, all that fear and loneliness and loss, grief and pain. I did feel some of the weight of all the things I’d heard. They were beautiful and vulnerable. It’s a privilege on one level to hear it. On another level, sometimes it felt heavy.”

Be warned then, The Boy, the Mole, the Fox and the Horse aims for the emotional solar plexus. The casting is powerful, too. The boy is voiced (beautifully) by Scottish newcomer Jude Coward Nicholl. The Fox is Idris Elba. “He is such a gravelly fox,” says Mackesy. “He’s terrifying and yet has the best lines in the film, though you have to wait for them. When I was on Zoom, directing with Peter, I kept thinking, ‘Am I really asking Idris Elba to say that again?’”

Tom Hollander is the cake-obsessed Mole. “Tom is such a genius, he can go from being comical to suddenly, for the payoff, ripping you down into the darkest place, just at the drop of a hat. It was such a privilege to work with him, to work with all of them.”

The giant but gentle Horse is voiced by Irish star Gabriel Byrne. Mackesy, who thought of his horse as Irish from the off, wanted Byrne in particular. “I sent him a letter, handwritten in ink along with a copy of the book, and said, ‘Do you fancy it?’” Not long after, Byrne rang from Ireland. “The voice went, ‘Hello, it’s Gabriel Byrne. I read the book you sent. Charlie, I am the horse.’”

The film is one of several versions of The Boy, the Mole, the Fox and the Horse. There have also been pop-up exhibitions and an audiobook recorded by Mackesy in his Suffolk farmhouse where – to keep out the noise of lawn mowers – he worked “in a pyramid made out of cushions in our barn”. Before that, when he was developing the characters, Mackesy would share images and dialogue on WhatsApp with friends. “We were all going through difficult things,” he says. “They’d look at what I sent and say, ‘That’s a bit trite’, or ‘That’s bollocks, you can’t say that.’ Or ‘God, yeah, I feel like that today.’

“I remember the first pop-up exhibition of drawings and the way men reacted to them. One guy had been brought in by his girlfriend. I was standing in the gallery, and he looked at me and couldn’t speak. He had tears pouring down his face. He just said ‘Thanks’ and walked out. Men often feel they have to appear to be strong, that it’s a failing to be weak – but you’re not giving up by asking for help. Better that than disappearing off this planet because you’re too ashamed to talk about it. I know many who have not been able to and they’ve gone.” Mackesy sounds, I say, as if he is speaking from experience. “I have lost quite a few friends over the years,” he says, “who’ve just found things unbearable.”

“Am I really asking Idris Elba to say that again?”

Among those he showed early drawings to was Bear Grylls. “I’ve known Bear for a very long time,” says Mackesy of a friendship that involved, at one point, both men rowing down the Thames together in a bathtub to raise money for a friend’s new prosthetic leg. “The brilliant thing about Bear is he’s far braver, fitter and stronger than I’ll ever be.

“I’m interested in my friends’ takes on existence and their views on different things, like what courage is. I know that for him, the bravest times have been when he’s gone through things and survived them and faced adversity. Then once we were talking about what the bravest things that I’d ever done might be and I knew that it was just daring to say help.” It’s a line that Mackesy gives to the horse in his book.

Ultimately, his message is a simple one: if you need help, then ask for it. If you are asked for help, then give it. “Christmas is a lovely time and it’s also a really tough time for many,” he says. “This year, given the state of things, it’s going to be even tougher. If the film can help in any way then I’ll be really pleased. It’s all I want.”

The Boy, the Mole, the Fox and the Horse will be released on December 25, 2022, on Apple TV+ in the U.S. and BBC One in the U.K.

Michael Hodges is editor at large for the Radio Times and a former executive editor at Time Out