The Boy, The Mole, The Fox And The Horse: Charlie Mackesy on seeing book come to life on screen this Christmas

Inspired by drawings he had first posted on Instagram, the heart-warming tale – based on four characters who share an unbreakable bond – explores themes of friendship and kindness through a series of brief but profound conversations.

The biggest selling adult hardback of all time earned British-born illustrator Mackesy a short film adaptation that promises the same magic on screen.

Reimagined in full colour with hand-drawn traditional animation, the BBC One special will take audiences on a poignant journey this festive season, as the foursome unite in the boy’s search for home.

Breathing life into the book’s protagonists is an award-winning cast of actors including Tom Hollander as the mole, Idris Elba as the fox, Gabriel Byrne as the horse and newcomer Jude Coward Nicoll as the boy. It’s a line-up Mackesy, 59, still finds hard to fathom.

“It blows my mind that I’m sitting here talking about a film which began with drawings, with little thoughts or fears, hopes, aspirations or dreams, that seemed to speak to people,” says the artist and author. “But here we are and I’m very grateful to everyone, however they contributed.”

His work is loved around the world and the book has struck a chord when it comes to mental health.

“(Mental health) is something I have struggled with,” Mackesy says. “My drawings were an honest, vulnerable dialogue that addressed some things. When I did get a reaction from clinical psychology hospitals, I remember thinking, ‘Really? OK. That’s great’. I didn’t think I would achieve that.

"I remember being at a book signing, one of the first ones, and there was a longish queue, and a boy was standing very quietly and looking at me. He had a book, I signed it, and he just said, ‘I just want you to know that your drawings have helped me stay’.

"I wasn’t quite sure what he meant by the word ‘stay’ and he said, ‘I’m still here’. I remember thinking, ‘Oh my gosh, if this helps one person, I’ll take that’. This 18-19-year-old boy is still around because of drawings I scratched out.”

The journey to screen was a “baptism of fire”, Mackesy says. “We had collaborative talks: How do [the characters] move? How do they look? How do they sound? Everything was up for discussion. It was just making a cake that none of us had ever made before, with ingredients that were new. And so, the cake took time.”

”My real journey was having to mark the animators’ work and send it back saying ‘Could do better’,” he continues. “I felt like a grumpy schoolmaster. But eventually I saw how this entire, brilliant team had learnt a language that we all speak now, in terms of movement and line. It was a learning curve for all of us.”

The Boy, The Mole, The Fox And The Horse airs on BBC One this Christmas.