In her 35-year career, the actor has seen the best and worst of Hollywood. She talks about divorce, depression and making her most personal film

Helena Bonham Carter does not attempt to disguise her hurt. She says she has just made the most important and personal film of her career, and is convinced nobody will see it. 55 Steps tells the story of Eleanor Riese, a psychiatric patient who successfully fought the US’s medical and political establishment in the 1980s for the right to refuse antipsychotic drugs.

Bonham Carter, who executive-produced the film as well as playing Riese, tried to get the movie made for 15 years, but it kept collapsing – budget problems, casting problems, director problems. Initially, she was going to play Colette Hughes, the campaigning lawyer (think Erin Brockovich) who represents Riese, with Susan Sarandon in the central role. But so much time passed that Bonham Carter ended up playing the older psychiatric patient, with Hilary Swank cast as the lawyer. And now the film is going straight to video.

We meet at a restaurant close to where she lives in London. You can spot her a mile off. If she weren’t so famous, you might think she was down on her luck – massive dirty black coat and trainers disguising a gorgeous floral dress (“I wore it as a tribute to Eleanor – she loves flowers”); massive shades disguising a gorgeous girlish face. Bonham Carter is the establishment’s oddball – uninhibited, direct, forceful, funny and, at times, vulnerable. (Riese was always an outsider, but they have much in common.)

She takes a bottle of Coke out of her bag, pours it discreetly into a glass and asks the waiter for ice.

“I want some food,” she says to me. “Have you eaten?” She puts on her filthy reading glasses, which are hanging on a pearl lanyard. Are the pearls real? “No, but they’ve got the weight. Feel them. Look. I’ve got to get them for Margaret, because she likes pearls.” She is playing the famously hot-blooded and hot-tempered princess in the next series of The Crown. She pulls a finger across her mouth to zip it. “I’m not allowed to talk about The Crown.” She turns her attention to the menu. “I’m going to do lots of meze. Aubergine salad! Mmmm. Tabbouleh, chicken shashlik, hummus, tzatziki and some lentils.” She bursts out laughing. “I’ll just buy the whole lot.”

Facebook Twitter Pinterest In A Room With a View, the 1985 Merchant Ivory adaptation of the EM Forster novel. Photograph: Allstar/Cinetext/C4

Bonham Carter, 52, seems to have been with us for ever. She comes from a well-to-do family (her great-grandfather was the Liberal prime minister Herbert Asquith), made her name in the 1980s playing English roses in tasteful Merchant Ivory adaptations of EM Forster classics (A Room With a View, Maurice, Howards End) and evolved into something entirely grungier. She first reinvented herself in the late 90s, cast as a louche siren in David Fincher’s Fight Club. Then came a professional and romantic relationship with Tim Burton, master of the ghoulish fairytale, who cast her in unlikely, often unearthly, roles – a rebel chimp in Planet of the Apes, the Red Queen with the huge, hydrocephalised head in Alice in Wonderland, the eponymous zombie in Corpse Bride, and the adorable serial-killer Mrs Lovett in Sweeney Todd. Bonham Carter and Burton had two children (Billy Ray, now 15, and Nell, 10) and became a tabloid staple. They were fabulously eccentric – supremely childlike (the goths who never grew up) and a Hollywood power couple. One day, Bonham Carter would be photographed shopping for milk in her pyjamas, the next she would be enjoying a New Year stroll with then prime minister David Cameron. (And, no, she says, she is not a Tory – “Rule of life: you don’t have to be a Tory in order to be friends with one. Even if they end up being PM.”) There were endless stories about their wacky lives – notably the fact that they lived in adjoining cottages, and slept separately (he snored in his sleep, she talked). Even she referred to herself and Burton as “the bonkers couple”. Then, four years ago, they announced they were splitting up.

“It’s a miracle this film got made,” she says of 55 Steps. “It’s fallen apart so many times.” But the more knockbacks, the more determined she was. She says she felt a responsibility to a woman who had been silenced for so much of her life. “It was like I was carrying the baton for Eleanor. The main thing she wanted was to be heard.”

The film is called 55 Steps because, among other things, Riese had OCD – she was an obsessive counter of her footsteps, and had to climb 55 steps for her first day in the San Francisco court. Has Bonham Carter ever had OCD? “No. I’ve had depression. My periods of depression usually relate to the end of things. But I don’t have rituals. I’ve had times when my mind is not helping me.” She stops. “Actually, when I was little, I did. I used to jump up and down three times. This was just before I did the 11-plus. I thought if I didn’t do it, I wouldn’t get in. It obviously worked.”

Facebook Twitter Pinterest Bonham Carter as Eleanor Riese, with Hilary Swank as her lawyer Colette Hughes, in 55 Steps. Photograph: Allstar/Mars Films

The curious thing is, she says, it only gradually dawned on her just how personal a film this is. She shows me a picture on her iPhone of her younger self, little more than a toddler. “I look so concerned. Already worried. I was a worrier.”

After the death of her grandfather, her mother, Elena, had a breakdown; Bonham Carter was five. “Grief can bring a hell of a lot of other stuff up,” she says. “But she always felt her breakdown was a gift. Mum has been a real example of wearing her depression and her mental frailty as a badge of honour. She’s saying: ‘Look at what I survived.’” (Her mother trained as a psychotherapist when she recovered, and still practises today at 84.)

When her mother had her breakdown, says Bonham Carter, “she had a recurring dream that she was eating her father – carving him up and eating him. She thought it was the most horrifying dream, and the therapist she ended up seeing said: ‘What did he taste like?’ And she said: ‘No one’s ever asked me that. Really sweet.’ After that, the dream went. Suddenly it was solved.”

The family links to 55 Steps run deeper. When Riese was 10 years old, she contracted meningitis, and an operation went wrong, leaving her with brain damage. When Bonham Carter was 13, her father, Raymond, a banker, was diagnosed with an acoustic neuroma – a noncancerous growth – in the brain cortex. The surgeon prolonged the operation by six hours to try to save his facial nerve; he subsequently had a post-operative stroke that left him paralysed and cortically blind. She adored her father. “He was amazing. He was so clever and flipping hilarious. When somebody is so disabled, other bits compensate. He got even brainier, and more bold. My dad sat down for 25 years of his life. He was never upright. The only time I saw him upright was when he came down the stairs in his mortuary bag.”

It was only when she was shooting a scene towards the end of 55 Steps that Bonham Carter linked her father’s experience with Riese’s. “I thought: ‘Of course I’m doing this film because of my flipping father; because he also had a medical intervention on the brain that went wrong.’”

The food arrives, with a glass of wine for me (Bonham Carter sticks to her Coke). “It’s so yellow!” she says. “It looks like a urine sample.” She gets the giggles.

Facebook Twitter Pinterest Bonham Carter in 55 Steps: ‘I was like, maybe they’re right, maybe it is completely over the top.’ Photograph: Allstar/Mars Films

She talks about how optimistic she was when 55 Steps was finished. It premiered at the 2017 Toronto film festival, the two real-life lawyers (Hughes and Mort Cohen, played by Jeffrey Tambor) attended the screening, and it got a rapturous ovation. “Mort came up to me and said: ‘You have no idea how much this is going to help; this film will do more to raise awareness of people like Eleanor than anything I can do.’ Then no one bought it.”

Why does she think that was? “One or two reviews were OK about me and another two really assassinated me. I was like, maybe they’re right, maybe it is completely over the top. There was one really horrible one and at the end of it somebody tweeted and said: ‘Excuse me, I knew Eleanor and she pitched her perfectly.’ When Colette saw the film she said: ‘You’ve resurrected her.’ So I felt a bit of vindication.”

Of course, it’s a big performance, Bonham Carter says – Riese was a big personality. “What I didn’t like about it was that they assumed I was being patronising. I am the last person to patronise this woman. I am her biggest champion.” Her voice rises. “Don’t you dare level that accusation. Maybe I’m a crap actor, but don’t don’t don’t say that I’m patronising her.” She is right; it is a big performance. But it is a big, touching, life-affirming performance that could just as easily have been Oscar-nominated as panned.

Bonham Carter says she thinks there might be another reason why the film wasn’t bought. “It might have been something to do with Jeffrey [Tambor], who has had a whole sexual scandal drama to do with the Amazon TV series Transparent. Unfortunately that came out just at the time, and people might have thought: ‘Oh, we can’t touch it.’” This year, Tambor was fired from Transparent after allegations of sexual harassment which he has denied. Bonham Carter is staying loyal to Tambor. “He has such compassion, and I don’t believe that same heart would be capable of any kind of abuse.”

A number of people Bonham Carter has worked with have been caught up in abuse allegations. Johnny Depp, who starred with her in five films Burton directed, was accused of being “verbally and physically abusive” by his former wife Amber Heard after they separated. Depp denied the allegations and Heard dropped her domestic abuse case against him. Did the allegations affect her relationship with Depp? “No. Johnny is still a friend. He’s the godfather to my children. I haven’t seen him for a long time. But he’s quite an elusive character.” Silence.

What does she think of the #MeToo movement? “It is definitely a good thing that #MeToo has happened. Any kind of abuse is not on. But I think one has to be careful. You have to be absolutely rigorous about what somebody has done to stand up and accuse them. You have to honour #MeToo.”

The #MeToo movement began on social media after the first abuse allegations were made against film producer Harvey Weinstein, with whom she has also worked. When I ask about Weinstein her response is typically measured. “Nobody is wholly bad and nobody is wholly good. He was very clever. There are a lot of reasons he was very powerful. He knew how to get you Oscar nominations. Both my nominations are due to him. And he had great taste in films.” What was the downside? “I found the way he treated certain people chilling – without any kind of respect. There were many times I disagreed with the way he behaved, and I don’t mean sexually.” He was bullying? “Yes. There were times when Harvey asked me to do certain things, and I said no. I knew I was running a thin line. Standing up to him wasn’t an easy thing to do because I knew I could potentially lose work.”

Facebook Twitter Pinterest With Johhny Depp in former Husband Tim Burton’s film, Sweeney Todd. Photograph: Everett Collection/Rex

Why could she stand up to Weinstein when so many others couldn’t? “Because I already had a career. Other people were employing me. I wasn’t reliant on him.” Despite this, she says, she did discover the cost of disobeying him when working on the Jean-Pierre Jeunet film The Young and Prodigious TS Spivet, about a genius boy who runs away from home. “Harvey wanted me to tell Jeunet to change it. There is a scene in which he hitchhikes and Harvey said as soon as that kid gets into a truck everyone will think the truck driver is a child molester and all the kids in America will be freaked out. I said: ‘I don’t think you’re right, and I’m not going to tell Jean-Pierre Jeunet I know better than him.’” What did Weinstein say to her? “‘You’ve got to tell that arrogant asshole he’s being a shit, he doesn’t know the American market like I do.’ I found it revolting.”

Did she think Weinstein’s behaviour would come back to haunt him? “No, absolutely not.” Because he was too powerful? “Yes.” Had she heard allegations of sex abuse? “I was aware certain actresses had had sex with him, but I thought it was consensual.” Did her experience put her off working with him? “No. It’s a business.”

Facebook Twitter Pinterest Bonham Carter: ‘It’s a loss of identity when you break up.’ Photograph: GP Images/WireImage

Bonham Carter is admirably honest about Weinstein. As she is about the end of her relationship with Burton. Reports have suggested they still live side by side in their adjoining cottages, but she says this is untrue. Earlier, she mentioned that she tended to get depression when things end. Did she have a bout after they split up? “I had a depression, definitely. I think when you’re with somebody your identity is wrapped up with that person, so it’s a loss of identity when you break up. I wouldn’t say divorce is the easiest thing.” Were they married? “No, but we were emotionally married. We’re family. So even when you know something is meant to end, that it’s had its proper life, you still have to grieve for all the good bits. It’s a whole massive re-formation.”

There have been rumours that they will get back together, but she says she now thinks of the relationship as the past. “I think we’ll have a friendship because we made the two greatest things in the world.” Do they share custody of the children? “Yes.” She pauses. “Well, they share us.” Is there anybody new in her life? She grins. “I’ve got two bunnies and a tortoise. I’m not prepared to talk about my friends.” Pause. That sounds like a yes? “Maybe.” She tugs at a huge silver hairpin that says “Maybe”. “Look there’s a Maybe in my hair.”

She talks about how the world has been turned on its head in recent years – Trump, #MeToo, Brexit (“God, it’s a disaster. Now we know what we’re talking about there’s no doubt we should have another referendum”).

After all the grieving, she says, she now feels positive. “I’ve got a whole new life. It’s fun. It’s less boring. It’s got a whole new unpredictability. It’s really nice.”

She is also excited about her work. While so many middle-aged female actors bemoan the lack of interesting work, Bonham Carter feels it is getting more interesting. After all the bonnets and Burton-inspired weirdness she is establishing herself as a character actor, with the rare ability to do frumpy (Enid Blyton and Riese) and glam (Elizabeth Taylor in the fine TV drama Burton and Taylor, and her forthcoming Princess Margaret in The Crown).

It is time to leave. But she is still thinking about 55 Steps. She says she knows it might sound funny, but she genuinely believes Eleanor Riese has helped her through her tough times. “I think it’s probably the best thing I’ve done. The irony is that I think three people will see it. But, luckily, even if you are in a nominal flop, as an actor you always have the gift of playing someone who’ll leave her imprint on your soul and psyche. I’m a wiser, more joyous person for having known her.”

55 Steps is available to buy and rent from 15 October