Orlando Weeks is describing the revelatory moment his father looked at the main character of The Gritterman, Weeks’s first illustrated children’s book, and saw his own dead father looking back at him.

Although unaware of the resemblance until that very moment, suddenly, Weeks – who has spent the last 14 years as the frontman of indie rock band the Maccabees – could see it too. “I wasn’t consciously basing the Gritterman on my grandad. But there’s something in the way he looks that you can tell ...” He trails off, struggling to pinpoint the exact similarities between his character, who spends the winter gritting the roads and the summer selling ice cream, and his grandad Bill, who repaired traction engines and heavy farming machinery in Devon and Cornwall, and who died in his late 80s when Weeks was a young teenager. “When I knew my grandfather, I felt that he had been a big strong man and now was less of a big strong man. Age had taken some of that broadness out of his shoulders. And there’s something about the way the Gritterman looks ... there’s a shadow of a bigger, stronger version of himself, in the past.”

The book – a touching Raymond Briggs-like story about an old man from a rural, working class neighbourhood, who is being forced by the council to retire from his job – might seem a surprising career move. But the public-school educated son of a public affairs consultant studied illustration at Brighton University, and was previously unable to figure out a way to combine his love of drawing and painting with his music career: “It’s something I’m annoyed I didn’t think of doing sooner.”

After the Maccabees announced they were splitting up a year ago, Weeks decided to work on a self-contained project to occupy his time before the band’s final gigs. The Gritterman was the result. It is accompanied by a soundtrack of original piano music and songs, which are written, played and sung by Weeks, and a reading of the book by the comedian Paul Whitehouse, who takes on the character of the Gritterman.

Weeks says the project was partly inspired by the similarity between his own circumstances and his father’s retirement. “I didn’t see my dad retire and think: right, I’m going to write an illustrated book. But I think it definitely played a part, along with beginning to question my own purpose and where my passions lie; thinking about how I fill my time, and seeing how he does. It’s very difficult, if you’ve invested in what you do, to allow yourself the freedom of not doing it any more, of not working all the hours that God sends.”

The plot follows the Gritterman on Christmas Eve, as he goes out alone to clear the snow one last time, before he must retire from the job he loves. “My dad was a lobbyist and worked in the arts. No night shifts,” he laughs. But when it comes to his grandfather’s physical, labour-intensive job, he acknowledges the similarities, and the Gritterman’s passion for gritting, in his trusty old van, seems to reflect Bill’s passion for repairing traction engines.

“Grandad would make his own bolts because no one else made them big enough. There were constantly these enormous greasy cogs on the kitchen table, even though he had a workshop in his shed. It was chaos in there, and it was incredibly cool. I remember it smelt like an engine, of grease. Everything you touched never came off you.”

He recalls how, on his sixth birthday, he was permitted by his grandad to sound the whistle on a traction engine, a type of steam engine once used to move heavy loads on roads and to plough fields. “At the time, I wasn’t aware it was such a sweet gesture on grandad’s part, to let me pull that whistle. But I was the first person to do it, on an engine he had been restoring for longer than I’d been alive.”

Although he is very close to his parents, he says, he struggled to get close to Bill. “He was pretty stand-offish. He didn’t talk much. I don’t even think I heard him say that many words. He was a gentle presence, and a very quiet man.”

Weeks deliberately made the Gritterman laconic, too. “The more economical I was with his narration and his monologue, the more licence I had to be expressive and flowery with the songs. I felt I could get away with that because the Gritterman is so closed and bareboned in the way he communicates.” He also allows his main character to be romantic about snow and winter – and then illustrates their isolating effects on a lone individual in an English landscape. “Hi-vis is not romantic. I don’t think those spinning lights on vans play into a picture postcard idea of English winter. I liked that. I liked that it wasn’t obvious.”

In his own lifetime, Bill’s work became obsolete, rather like the Gritterman’s job in the story. “Got a letter from the council: Dear Sir... your services are no longer required,” the Gritterman recounts, adding: “I read somewhere that there’s a tarmac now that can de-ice itself. I’m not sure I want to live in a world where the B2116 doesn’t need gritting.”

On the Maccabees’ first album, Weeks wrote a song, Good Old Bill, about his grandfather’s death. Listening to it now, the chorus line, “The engine won’t start without him”, seems to take on a new significance. Weeks explains the inspiration for the song: “My grandad left one of his traction engines to a steam museum in Cornwall. In his final years, he’d go and visit it and help with the upkeep, that sort of thing. On the day he died, my grandmother got a phone call. It was the museum. For the first time, the engine he’d donated wouldn’t start.”

So what would his grandad think of the book? “I expect he would ask me: where is the manual where you learned to do this? He would find it odd that you just kind of do it, with your fingers crossed. But I know he would have respected how I feel about my work. And I think he would have been proud of me, and hoped that I was happy. He was a very kind man.”

• The Gritterman is out now, published by Penguin. The album is available via download and music streaming services.