Eighteen years after Frasier ended – and nearly 30 since it began – it’s finally happened. David Hyde Pierce has found a major role rich enough to tempt him back to TV. Not Niles Crane again – not yet, anyway. To sate fans early: Pierce is thrillingly noncommittal about Kelsey Grammer’s reboot: “It’s happening, but I don’t know in what form, and I don’t know when, so I don’t know where I’ll be and what I’ll be doing. I’m certainly interested to see what they come up with.”

Which definitely isn’t a no. But before then, at least, he’s found someone worthy of his time. Someone not a million miles from Niles, in fact. In Julia, the deluxe new Sky/HBO series about hulking TV chef Julia Child (played by Sarah Lancashire), who popularised French cooking in 1960s America, Pierce stars as her husband, Paul. Paul is a snob. Fastidious, a bit weedy. He knows his burgundies and will eye-roll if you pair boeuf with beer. He’s sometimes insufferable. We come to care for him deeply.

So far, so older version of Grammer’s pernickety sibling. And yet, the more you watch Julia, the more Paul seems a different species. “Niles is a person who lived in spite of his body,” Pierce explains patiently. “And Paul is a man who lives completely in his body.” It’s true. Niles thrummed with lust and tension. Paul is so relaxed he practically waggles.

As for Pierce: well, I can only see his head and shoulders over Zoom, but they seem well-adjusted enough. It’s the day after his 63rd birthday and he has slightly sparkly stubble and wide eyes that skate from side to side as he composes his answers. He is smart and agile and funny.

Yes, he says, he’s aware of the similarities. “Both shows are about family. About people who are literate. Written by people who are literate. Yet they are also both very accessible and not highfalutin.”

Frasier was proudly erudite and enormously popular: huge ratings, 37 Emmys, four for Pierce. He knew it had been syndicated when a refuse collector yelled “Niles!” at him in the street. “I thought: OK, I bet that’s someone who did not think of Frasier as appointment TV. But now it must be coming on at the dinner hour. People who might not have thought this was a show for them go: ‘Oh, I get this.’

“That’s very exciting to me. The same thing can happen with Julia. You won’t need to be a Julia Child fan or obsessed with French food to go: ‘Oh, this is really interesting.’”

There’s certainly lots to get your teeth into. The Childs’ marriage, for starters: no kids, few regrets, plenty of necking. “You look good enough to eat,” Julia tells Paul in the opening scene. Both parties are keen guzzlers, appetite only lightly dimmed by menopause. “The line between food and sex was indistinguishable for them,” says Pierce. “I don’t mean they had inappropriate relations with food. They were sensual people.”

To tap into that, Pierce took up drawing; Paul turned to art in retirement. When sketching, he says, “time stops around you. There’s something very literally sensual about that. Your senses are feeding you.”

What does he draw? Anything. He glances about but there are no examples to hand. Nothing on the wall, either. His apartment is not hectic: he’s precisely aligned between two blank white doors. The effect is half Beckett, half Brian Rix.

He’ll sketch whatever’s there, he says. A glass. Bread. Himself? Only once. “One half seemed extremely accurate and the other half less so, and there’s probably some drawing reason for that. Or it reveals some deep psychological secret.”

The other day he uncovered a portrait he’d drawn, aged 16, of his father. “I was floored to re-establish connection with my younger self!” He describes it excitedly: his father, glasses on, reading the paper.

“I clearly loved the man. And if you look at Paul’s artwork – and especially his photographs of Julia – it’s pure love.”

And it is this – more than the snootiness – that really unites Paul and Niles. Their devotion to another person: in Niles’s case, Daphne, the daffy physical therapist played by Jane Leeves. Is he especially good at tapping into that?

“Well, I have done it in real life. I’m completely devoted to one person, so I know what that feels like. It’s also the example I grew up with with my mom and dad. So it’s instilled in me.”

Pierce was born in Saratoga Springs in upstate New York in 1959, the youngest of four children. His parents, Laura and George, were insurance agents. As a boy, he dabbled in Gilbert and Sullivan and enjoyed theatrically chucking himself down the stairs. He studied music at Yale then, realising he wasn’t quite concert pianist standard, switched to English and drama. The first decade of his career was spent juggling Broadway bit parts with selling ties at Bloomingdale’s. At one audition 40 years ago, he met another actor, Brian Hargrove; they’ve been together ever since.

“We kept trading places in terms of who was more successful, who was bringing in the money. Being on a big national television show for 11 years, I ended up with more public recognition than Brian [who moved into TV writing], but through all of that we have been able to always be there for each other and support each other. With not a lot of hassle, I have to say.” Why? “We were made for each other,” he says, matter-of-factual.

“They’ve always been wonderful partners,” says Harriet Sansom Harris. She’s worked with them at every stage: that first third, the Frasier years (best known as ruthless agent Bebe Glazer on Frasier) and during Pierce’s wildly-stacked theatre run ever since. “Always in tune. They thrive on each other’s company. They just trust each other so much.”

Rehearsing the musical It Shoulda Been You with them a few years ago – Pierce directing Hargrove’s script – the most negative feedback she ever heard them exchange was: ‘Well, I’ll have to think about that.’

So when Pierce calls the Childs “one mutually sustaining organism”, he knows his stuff. The timing of Julia’s sudden fame was crucial, he thinks. “It wasn’t like they were kids in their 20s and suddenly one of them’s in Titanic. It was yet another chapter in a well-written book.”

His own narrative was a touch more meta. When Frasier took off, paparazzi started snapping him and Hargrove walking their dogs. Interviewers asked if he was dating anyone. “My life is an open book,” he would reply, “just don’t expect me to read it to you.”

It wasn’t until some three years after Frasier ended that he began explicitly mentioning his partner, who became his husband in 2008, around the time of California’s flip-flopping over same-sex marriage ban Proposition 8.

“When you’re working in the theatre,” he says today, “whatever your private life is, no one cares. There’s something about that medium of television, maybe because it has to be marketed in such a massive way, that suddenly the behind-the-scenes on the set, the behind-the-scenes in your life, what happens behind your curtains, becomes part of the story. That was a shock to me.”

In fact, all those stories have been happy ones. The cast of Frasier were notably close. Grammer calls Pierce the brother he never had. Along with the late John Mahoney, who played their dad, Martin, Pierce is godfather to Leeves’s son.

“David is a very easy person to love,” emails Leeves. “He makes everyone around him better.” She doesn’t just mean professionally. “He has a rare mix of generosity, compassion, intelligence and elegance.”

Adds Joe Keenan, one of Frasier’s chief writers: “I’ve never worked with another actor who combines his amazing technical virtuosity for comedy – split-second timing, micro-nuanced facial expressions – with emotional honesty.”

“He helped give Frasier a tonal range that could swing from farce to heartbreak, sometimes in a single episode, and made even the wildest flights of comic absurdity (like fainting at the sight of blood) feel totally real.”

In Frasier, Pierce gives perhaps the most exquisite sustained sitcom performance of all time: incredibly funny, stupidly moving. An immaculate balance of what Samson Harris calls “flights of fancy and perfect taste. He’s sort of a self-calibrating element. Always placed perfectly.”

His comedy heroes, he says, are Alec Guinness (for the dryness and subtlety), John Cleese (maniacal conviction) and Buster Keaton (unflappable deadpan) and something about the alchemy is golddust.

Rewatch the show today and it can feel breathtaking, not least for how it queered the pitch of mainstream comedy; satirising intolerance while poking affectionate fun at everyone. Thanks in large part to Keenan’s landmark episodes – The Matchmaker, Out With Dad, The Doctor is Out – there’s an ease with sexuality as well as a willingness to joke about it that feels revolutionary.

When I suggest Frasier changed the world – without quite explaining why – Pierce scoffs delightedly. Yet he more than most must be forever reminded of its impact. Walking around New York once, says Sansom Harris, he was accosted by love-bombers on every block. “He was so sweet to them all. He said: ‘This could go away in a heartbeat.’ He treats people with a great deal of respect and expects it, too. He would probably be quite taken aback if somebody’s not polite. He would wonder why in the world somebody would behave that way.”

Plus, he’s a committed cheerleader for the arts, and becomes especially animated about a cellist he saw playing Bach on the streets of Ukraine. “There’s a reason. There’s a reason Yo-Yo Ma played Bach cello suites in the midst of the pandemic. The sparest, most elemental kind of music that you wouldn’t think of as popular entertainment – because it wasn’t, it was lifeblood.”

Music is more fundamental to him than acting, he explains, slightly bashfully. But TV did “come to the rescue” during the pandemic for him, too. Not reality TV – “naked people in swamps eating bugs. I can get that at home”. And not comedy, either, it turns out. In fact, it was live streams of St Luke’s string quartet.

Still, lockdown offered a chance to reassess his life and left him with renewed enthusiasm. “It makes me nervous to talk about it as an opportunity, because it was a disaster. A catastrophe for the world and will perhaps continue to be. So it seems cavalier to even talk about what I got out of it.

“But amid colossally awful things like the pandemic or the war, you are also reminded how desperately we need the stuff that keeps us going.” Plus, he adds, “in this country at least, we don’t think about death. No one talks about it until shockingly, someone dies, and in some bizarre way, you feel like: ‘I had no idea that could happen!’”

Covid changed that. Though, actually, not for him: he’d already had multiple wake-up calls – with friends in the 80s and 90s, then losing his father and grandfather to dementia – he’s done a lot of campaigning since for the Alzheimer’s Association. His father died in 1998; his mother three years before.

“I take nothing for granted. But I think that might just be anyone who gets to my age, who’s been paying attention. You see a lot of stuff happen, to people that you love or to you, or you see it happen to the world. The trick is to stop being surprised, but you never want to stop caring.

“When you first lose a parent, it’s unthinkable. Like an earthquake. Then as you go on you realise: ‘Oh, this is a thing that happens. Wow.’”

There is silence. I can’t help but remember what he said about being half an organism. Doesn’t that make the future frightening? A pause. “I don’t know what I would do without Brian, but that doesn’t blind me to the fact that one day death will separate us.”

He smiles, polite despite depressing questioning. “I feel like what makes life precious is its vulnerability. Like a china cup. Part of its value is that we only have it for a short time. Which is why I love things like the arts. Anything that causes us to appreciate the moments, because we won’t have that many of them.”

Julia starts on 12 April on Sky Atlantic and Now