Emma Hughes talks to the actor about Withnail & I, singing for his supper – and sniffing trees.

Richard E. Grant is the godfather you never had – the one who’d have sent you hampers from Fortnums once a term and opened Champagne on the slightest pretext. He would never, ever have forgotten your birthday. The first thing I notice about him is that he really, really wants everyone around him to be having a good time – a rare quality in an actor. The second, even more unusually for someone in his profession, is that he gives the impression of never quite being able to believe his luck.

“I’m 60 in two blinks and I’m absolutely astonished to be working as much as I am,” he says earnestly. As we speak, he’s flinging things into suitcases ahead of a six-month stint in America. He’ll spend half that time filming Can You Ever Forgive Me, playing Hollywood biographer-turned-forger Lee Israel’s cocaine-addled sidekick. Then, it’s off to Chicago, where he’ll be starring as Henry Higgins in My Fair Lady.

‘The opportunity to do a musical with a full-sized orchestra was irresistible’

It’s the second time he’s taken on the role; his first Prof Higgins (Sydney, 2008) got rave reviews.

“On the opera circuit, if you’ve done it once and didn’t fall off the stage, they’ll ask you to do it again,” he deadpans.

“And you don’t have to be a great singer to play the part. My wife [Joan Washington, who he married in 1986] is an accent coach – a female Henry Higgins – so I’ve sort of been around it for a long time.

“Also, the opportunity to do the musical with a full-sized orchestra was absolutely irresistible. T. S. Eliot said it was actually an improvement on Shaw’s already brilliant play, so it has a very high pedigree.”

As does Mr Grant. He became a confirmed national treasure when he appeared in the fifth series of Downton Abbey (as corridor-creeping art historian Simon Bricker), but, unlike some of his contemporaries, he keeps people guessing. He’s worked with everyone from Martin Scorsese to the Spice Girls; his new film, Jackie, an all-star biopic of Kennedy’s widow, opened in the UK last week. He’s playing Bill Walton, the painter who masterminded JFK’s funeral.

‘The city was in complete lockdown’

Making the film, he says, was a ‘monastic’ and humbling experience. “We started filming in Paris two days after the 2015 terrorist attacks, so the city was in complete lockdown, plus Pablo Larraín, the director, likes to work in near silence. The combination of that, plus the subject matter… Nobody was sitting around having a laugh.”

Jackie is an Academy Awards frontrunner; Mr Grant describes Natalie Portman’s performance in the title role as “truly extraordinary”, but bats away any suggestion that his own star is in the ascendant across the Atlantic.

“English actors are more willing to play unsympathetic parts than our American counterparts – and we’re much cheaper. It’s all such a confluence of luck, availability and chance.”

Things could so easily not have come together for him. Born Richard Grant Esterhuysen in Swaziland, he moved to England in 1982 and spent years trudging around the audition circuit – his father told him he’d end up tearing tickets at Waterloo station. Then came Withnail and I and the chance to play the elegant waster of the film’s title.

When director Bruce Robinson found out Mr Grant was teetotal (he’s allergic to alcohol), he made him go on a 12-hour bender that ended with him projectile vomiting all over Shepperton Studios. His efforts paid off: 30 years on from the film’s release, Withnail is one of the immortals.

“Hand on heart, there isn’t a single day that goes by when I don’t have someone quoting a line from it to me,” he says.

Some actors might get sniffy about their best-known film being one they made nearly half a lifetime ago. Does it bother him? “No, no, not at all. I’m just glad I’m still vaguely recognisable as the person who played that part.”

‘The seasons in England are extraordinary. I know we moan on endlessly, but I love them’

What will he miss while he’s away? “The humour and the weather,” he says immediately. “Not allowing anything to be taken too seriously is our saving grace. And the seasons in England are extraordinary. I know we moan on endlessly, but I love them – I absolutely revel in it, all of it.” He lives opposite Richmond Park and can’t get enough of the smell of the oaks, the moss and the leaves when it rains.

Frosty Britain - Andy Thomas

Richmond Park – Andy Thomas

That brings us onto the other string to his bow. In 2014, he raised eyebrows by announcing that he was launching a perfume, Jack. Celebrity fragrances tend to end up in the bargain bin, but his, it turned out, wasn’t to be sniffed at: it’s an earthy, grown-up blend of citrus, pepper, vetiver and (in what he insists wasn’t a nod to Withnail’s infamous Camberwell Carrot) marijuana notes. He has a successful range stocked in Liberty and his daughter Olivia works with him.

‘Yes! Absolutely! Bullseye!’

With a brand to build, he’s had to join Instagram, but @richard.e.grant (“Sniffer of all things sniffable, bed jumper, actor, writer, dad, husband”) seems at ease posting pictures of his garden and dinners for his 10,000 followers.

Perhaps it’s because he’s a natural enthusiast: when I put forward a tenuous hypothesis that Withnail and Higgins share a kind of restless, manic energy, he seems genuinely delighted by it (“Yes! Absolutely! Bullseye!”). Or perhaps, as a long-time juggler of plates, he’s better suited to documenting his life online than most actors.

Doesn’t he ever want to just lie down for a bit? “I think it’s in my DNA – I like to have days crammed with dozens of things to do,” he admits. “My father said to me when I was nine that I was like an overwound clock. On Jackie, Pablo was constantly telling me ‘Be as still as you dare to be’ and it felt completely alien. Even when I thought I was like a tombstone, he would say ‘Less, less’.

“I’ll probably crash and burn when things come to a stop,” he tells me – so cheerily that I can’t imagine it’s going to happen any time soon. Then, he’s off, to try to cram even more into his bursting suitcases.

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Richard E. Grant, 59, can be seen in the film Jackie, which opened this week in cinemas nationwide, and in My Fair Lady at the Civic Opera Building, Chicago (April 28–May 21, lyricopera.org)