"I love death," says Everett nonchalantly. "And I love deathbed pictures ... and deathbed rooms.

"And so when I thought of trying to perform Oscar Wilde, mainly because I thought it would be a great part for me, I was trying to think how to make it in a room that expanded and shrank into various scenes that his brain passed through as it crumbled and died."

Everett, whose two volumes of scurrilous autobiography had already demonstrated his deft way with a pen, wrote it himself. After trying unsuccessfully to find someone he liked to direct it, he decided to do that too.

Actually, it is a bit misleading to say it covers three years of Wilde's life, because the narrative wanders – along with the subject's dying mind – between present and past, the real and the imagined, making it less of a biopic than a life mosaic. Most of it is shot hand-held, which Everett felt gave the film a sense of intimacy but also had the advantage of being much quicker and thus cheaper than fixed camera set-ups involving tracks on the floor and lens changes. He didn't want it to look like that, anyway.

"When it became static and conventional, it turned into Downton Abbey," he says. "I wanted it to look lovely and have great costumes and to have sparkling, witty dialogue, but I didn't want to dwell on any of it. I wanted to drive by it all." As he said elsewhere, he wanted it to look like a ride on a ghost train.

Death has often filled Everett's thoughts. For the first few years of the AIDS crisis, he says, he lived in a state of terror. At 16, he had dropped out of his venerable Catholic boarding school, gone to London and plunged into London's gay scene. When he was at drama school, he worked as a rent boy – "I was such a slag and a slut in the '70s" – and was a leather queen for fun.

In 1983 he saw one of his many former liaisons in the news as one of the first men in Britain to be diagnosed with the new disease. He was just about to film Another Country (1984), the film about the Cambridge spy Guy Burgess that made his name. After that, the deluge. "Lots of people that I'd been with were dying," he told The Guardian. "And dying in a most terrifying way. Of every 60 seconds, 30 were in sheer panic. Especially being in front of a camera; I lived in fear of a cameraman saying: 'What's that on your face, Rupert?"'

He behaved badly on Another Country and worse when he went to film Dance with a Stranger (1985) with Miranda Richardson, throwing his weight around in a way unbecoming to anyone, let alone a newcomer as wet behind the ears as he was. By his own admission he was "a catastrophe"; his newly minted career was over almost as soon as it had started. It wasn't until 1997, when Australian director P.J. Hogan cast him as Julia Roberts' mate in My Best Friend's Wedding, that his particular louche charm found favour again. Because terror, he says, makes you behave strangely.

It was another death, however, that provided grist for his approach in The Happy Prince. In 2009 he watched his beloved father – a gruff naval officer, but one prepared to tolerate his son's childhood cross-dressing – drift away.

"It was fascinating. This sounds awful, but I adored my father's death in a way. Being with him and noticing everything that was going on in it. He was very old, so it was good to die. But when the brain starts crumbling, everything changes. Your sense of distance, for example; you suddenly become miles further away from me, because the brain isn't getting enough blood. Then the speech starts becoming funny and you start having memories that look like they're happening in the room. I thought 'oh God, this is amazing! It would be so amazing to try and capture this somehow.'"

That became his deathbed script; he then began his search for a sympathetic director. "That process took about two or three years. Getting scripts to good directors through management and agencies, that's like getting into Fort Knox. You don't realise what it's like until you try and do it, but it's a head-f--- of enormous proportions."

Of course he was famous but, after years in a wilderness of being gay, middle-aged and – even though he never did have HIV – still something of a nightmare, not nearly famous enough.

"If I'd done it 10 years before, when I'd just done My Best Friend's Wedding, I probably would have got Steven Spielberg. But after that, you know, my star had sort of regressed towards the Crab Nebula. So I decided to do it myself."

That didn't make it any easier to get rolling. Even with his friend Colin Firth signed up for a supporting role, he couldn't put a deal together. Perhaps, he reasoned, people just needed to be reminded of how very obvious it was that he was born to play Oscar Wilde. To that end, he took a production of David Hare's The Judas Kiss to New York, working with "a great Australian director called Neil Armfield". It did the trick, more or less.

"I managed to start getting deals, but even then!" He groans theatrically. "Oh God, it was up and down, it was coming and then it didn't come." In retrospect, perhaps that was a good thing. "It became a sort of lifeline. I think the reason I got it done is because it became my whole life."

In a few of his more rashly expansive moments, Everett has said that he has made Oscar Wilde his personal Christ figure, which is actually not unusual: Wilde has been sanctified, if not deified, by many gay activists. But one of the things that is so good about The Happy Prince is that Everett does not paint him as a saint.

"But I don't think Christ needs to be saintly!" he says. "Christ is just a mixture of humanity and godliness. Genius and earthiness. I think we've never investigated the Christ idea. It's such a fascinating notion."

And it is fascinating, like so many of Everett's conversational byways, but we must move on. Oscar Wilde could likewise be kind and compassionate "but also incredibly selfish, egocentric, snobbish and greedy". Suing his lover's father, the Marquess of Queensbury, for libel – because he had left him a note describing him as "a somdomite (sic)" – was rank arrogance. Actually, it was crazy. "He was such a big star, he just thought the whole world was in his hands. It's a typical celebrity madness he suffered from."

The case closed and a warrant was signed for his arrest; Wilde could have escaped, but chose prison and martyrdom. That's where Everett, who was raised a Catholic, sees a parallel with Christ's passion.

"He sacrificed himself to keep his work alive, I think," he says. "Like Jesus on Palm Sunday. I think he realised that if he ran, his relevance would be finished."

Small wonder that Everett feels such kinship with him. His own tantrums are spectacular, his attraction to A-listers unembarrassed, his subsequent skewering of these fairweather friends hilarious; he seems to be simultaneously one of them and one of us.

A typical episode in Vanished Years (2012) is his account of waiting on Henry Kissinger at a party held by former Vanity Fair editor and New York aristocrat Tina Brown. "With success comes compromise, and it's amazingly easy to forget 2 million massacred Cambodians as one is passing round the cheese straws."

Compromise is not the same thing as tact, however, which means that Everett has repeatedly plunged himself into hot water with casual digs at gay dads, transgender teenagers and erstwhile friends such as Madonna, who dropped him as her bestie after he described her pleasuring Sean Penn under the tablecloth at dinner in his first book, Red Carpets and Other Banana Skins (2004). She was furious; he worked up some fury in response; in the process, he recognised the toxicity of that friendship.

"Because what happens with all big stars, is that they are energy eaters," he said later. "They just look at you and – schlloooop – you end up as a kind of crumpled loo roll."

More usually, he simply shrugs these things off. He might regret screaming at a backstage dresser, but he can't say he won't do the same thing again. He supposes that, like Oscar Wilde, he has sabotaged himself along the way. Certainly, he has experienced some spectacular vicissitudes of fortune; at one stage he resorted to doing television in Russia.

"It's like snakes and ladders. Career death is rather like real death, so it gives you an opportunity to see what real death feels like. One minute, you're careering round the corridors of power, and everybody's going: 'That's a fabulous idea'. The next minute, you're still careering around but everybody's walking right through you. You've died and you didn't realise." Death again, you see: it's the one certain thing.

Today he doesn't feel inclined to take all the blame, however. Coming out as a young man – he was only 21 when he made Another Country – effectively stalled his career. "It's not an ideal thing to be gay if you want to go for the high wire in show business," he says. "You meet a brick wall at a certain point." Nobody would ever ask a gay man to be James Bond, he said when the role was coming up for renewal, no matter how much of a shaken-not-stirred man he might be in every other respect. That may be true, but he also has that diva reputation flouncing before him. I remember interviewing gay activist Ian McKellen not long after this made headlines. He raised one eyebrow. "Do you think that's the only reason?"

Playing Wilde staggering round the streets of Paris "as a boozy vagabond, smelling vaguely of sweat, cigarettes and urine, lurching from cafes to bars, cadging drinks, a charming Irish tinker": this is unquestionably Rupert Everett's signature role. I wonder if his view of Wilde changed over the decade he worked on the film.

"No," he says. "Because he became me. Or I felt I became him. It's peculiar. Sometimes I felt I was pushed by a mystical force."

Oscar Wilde believed he saw ghosts, including his wife's on the night she died. In an apartment in Naples where Wilde once lived, Everett felt Wilde telling him to keep going. So he did. "Yes, I'm a Catholic," he laughs. "What can I tell you?"

The Happy Prince screens as part of the British Film Festival, until November 14. britishfilmfestival.com.au