“Look, there’s a xylophone and a scrapey and a bang and a tambourine and all sorts of different things. So that’s been my object of decision for the last 30 minutes.”

Such innate musicality has won Collier a following that ha grown steadily since 2012. That year, the boy opera singer turned autodidact uploaded a couple of Stevie Wonder covers to YouTube in which he harmonised with five other versions of himself and played a dozen instruments.

Herbie Hancock, Pat Metheny and kd lang were among those leaving glowing comments as the videos went viral, as was a guy who knows a thing or two about child prodigies — Quincy Jones, who with Michael Jackson produced Thriller, the biggest-selling album of all time.

Collier had the audacity to turn down Jones’ offer to produce his own debut album, 2016’s In My Room, but he did sign up to Quincy Jones Productions for management.

“I managed to see Quincy a few months ago — he came to my show in Los Angeles. What a privilege to get to hang out with him,” he says of the 89-year-old.

“He’s like the purveyor of ultimate wisdom, but he keeps telling me he’s just getting started!”

For an artist whose career really is just getting started, Collier and his Quincy connection and undeniable talent have won him big milestones. Two nights before our call, he’d played piano to 90,000 people at Wembley as a guest of Coldplay.

What Collier hasn’t achieved yet is the big, Quincy-style hit single that might expand the audience for his records beyond the jazz heads and music students that dominate it today.

He came close with 2020’s Sleeping On My Dreams, from the third instalment of his multi-genre Djesse album project (whose fourth and final part will be released next year, and presumably contain songs in hitherto unknown keys).

Collier could not help interrupting the song’s infectious R&B flow with a psychedelic pre-chorus that sounded something like a barbershop quartet attempting a Bach chorale. Arguably, this complicated bit was to blame for the single’s streaming count being measured today in seven figures instead of nine.

But Collier is unrepentant.

“I think it’s always dangerous for creative people to be creating music as ‘pop’ music,” he says.

“By default, it’s going to be music that appeals to the widest number of people, which often means that it doesn’t go as deep as it can go ... I’ll always be a sucker for those technicolour multiple layers, things that are rich and dense, and I think the job of artists is to follow their goosebumps and see where they take them.”