Hugh Grant learned some years ago that if a filmmaker doesn’t make something from the heart, it shows. The films that work best, and are most loved, he’s found, are the ones that the directors really meant.

It applied to his romantic comedies with Richard Curtis as well as “Paddington 2.” And he’s pretty sure it’s true of “ Wonka.” The lavish big screen musical about a young Willy Wonka — before Charlie, before the chocolate factory — is dancing into theaters this month with its heart on its velvet sleeve.

Like the “Paddington” movies, “Wonka” was dreamt up by Paul King, a lifetime Roald Dahl fan and a writer and director whom his collaborators somewhat universally agree may actually be Paddington in a human costume. With a beloved troupe of actors, including Grant, Timothée Chalamet, Olivia Colman, Sally Hawkins as well as newcomer Calah Lane, its vibrant costumes and sets and a contagious “let’s put on a show” energy, “Wonka” feels like a modern homage to classic MGM productions of the 1940s.

But King wasn’t so sure about “Wonka” at first. He worried that like so many other “brands,” a young Willy Wonka movie was something devised in a boardroom with visions of “12,000 movies and a TV show.”

Then he went back to the book, which he’d read so many times as a child that the pages fell out of the spine. This time he found not just a great character in Willy Wonka, an unapologetically flamboyant dreamer whom Dahl also seemed a bit obsessed with, but also a breakthrough about his work.

“I realized how informative Dahl had been to everything that I love about family movies. They’ve got these great heightened characters, but there’s a real beating heart to them,” King said. “It was like, oh this is the mothership.”

And, with his “Paddington 2” co-writer Simon Farnaby (of “stop that stunning sister” fame), he would spend years toiling over what they’re calling a companion piece to the Gene Wilder “Charlie and the Chocolate Factory.”

Chalamet, the wildly popular Oscar-nominated actor of “Call Me By Your Name” and “Dune,” wasn’t technically a song and dance man (though his digital footprint from his teen years contains some evidence to the contrary) when he signed on to play Wonka. But King was convinced that he was the perfect person to balance “sincere” and “ridiculous” thanks in part to his memorable (and “hella-tight”) performance in Greta Gerwig’s “Lady Bird.”

This was a little baffling to Chalamet, who only learned this at the premiere in London. But for him, “Wonka” was a chance to do something a bit different, on a grand scale. He also understands audiences being a little skeptical of any spin-off of a beloved character, but he takes comfort in something Gerwig said while they were making “Little Women.”

He recalled her telling him “something like, ‘For anybody that’s saying that a lot of versions of this have been made, you know, when it’s done well, no one complains,’” he said. “I think Paul really did that here.”

In addition to “Pure Imagination” and the Oompa Loompa song from the 1971 film, Neil Hannon, frontman of The Divine Comedy, wrote six original songs, while Christopher Gatelli (“Hail, Caesar!”) oversaw the choreography.

Though Chalamet grew up surrounded by dancers (his sister, mother and grandmother included), and had done musicals at his performing arts high school, he didn’t fully appreciate the exhaustive rigor of it. He’d trained for “Wonka” for months, but he was still not fully prepared for how taxing “take 13” of a large-scale dance number would be.

“He’s very modest and I think that’s one of the nice things about him,” said King, who has compared Chalamet’s singing voice to Bing Crosby.

The sets, overseen by production designer Nathan Crowley (“Interstellar”) were also something grand to behold. King wanted the city to look like “the best of Europe.” In total, they built more than 50 set across three soundstages, a backlot and an aircraft hanger around Warner Bros. Studios Leavesden, in addition to several on-site locations in the U.K. to give the film its whimsical, but grounded feel. Lindy Hemming (“Paddington”) designed the vibrant costumes.

Perhaps the most inspired twist of “Wonka” is Grant, an actor made world famous for his good looks and charm and romantic leads, who is playing an Oompa-Loompa.

King had already introduced Grant to a new generation of youngsters having him as the washed-up actor Phoenix Buchanan in “Paddington 2.” When he was re-rereading “Charlie and the Chocolate Factory” he found “Hugh’s voice” coming into his head for the devious little workers.

“They’re so biting and satirical and funny, but they’ve got a real kind of edge to them … and they take an enormous delight in these children’s demise,” King said. “I had this vision of Hugh Grant, you know, this high with orange skin and green hair. And once you have that picture come into your mind, you have to try and get it out there.”

Grant is also a self-proclaimed miserable curmudgeon, which he’ll say with a straight face right before saying something completely contradictory. In his interviews, which often go viral, he’s witty and wry and reliably unreliable.

Yet when he talks about King, and “Wonka,” and it all being from the heart, something melts away.

“One of the things that made those romantic comedies that I made with Richard Curtis work, apart from the fact that he’s very good at writing comedy was that he meant it. He really cared about love and he was always falling in love, falling out of love and being traumatized by it. But he meant it,” Grant said. “Paul King means all this. The message of Paddington and the message of this one, you know, family matters, the people you share your chocolate with. It’s not a trite, tacked on motto. It comes from his heart.”

And it’s easy to believe that Grant, miserable though he may be, actually means it too.