On a shelf in Brian Blessed’s study is a plastic toy, a replica of himself as Prince Vultan in the film Flash Gordon. There is a resemblance but, with this actor, the very idea of a miniature seems wrong.

The mountainous original is sitting at his desk, wearing a striking winter morning costume of red fleece, pyjama bottoms and wellington boots. He must be the hairiest 83-year-old man in existence, his huge head crowned by a thick grey thatch, his neck Tudor-ruffed by what seem metres of white beard.

“Kenneth Branagh sits every week where you’re sitting!” he booms.

The actors met 30 years ago when Blessed was cast in Branagh’s film of Henry V. Both now live on the Surrey-Berkshire borders, which allows for regular catch-ups. “It’s a father-son relationship. He’s the father and I’m the son!” declares Blessed, a gag he has used on the TV chat-show circuit and in the autobiographical one-man show he tours around the UK.

Nicknamed Big Yeti … Blessed on an expedition to climb Everest in 1993. Photograph: Steve Back/ANL/Rex/Shutterstock

The agenda in the Blessed-Branagh gatherings apparently has the older actor discussing his plans for terrestrial and extraterrestrial expeditions – Blessed is an Everest-level mountaineer and has undertaken astronaut training in Russia – while the younger man seeks advice on showbiz projects, such as the movie of Agatha Christie’s Death on the Nile that he is currently shooting at nearby Longcross Studios.

“You’ll see it from the motorway down there!” An extravagantly pointed finger threatens to remove the eye of a nodding plastic doll of the 14th Dalai Lama, whom Blessed counts as a friend. “Branagh’s rebuilt fucking Egypt!”

“Will you work with Branagh again?” I ask. “I hope not!” roars Blessed. “Why hope not?” “Because we’ve done five films over the years and my friendship with him is much more important than being in films. So we have an agreement that he never directs me again.”

Blessed lives in a secluded long, low house filled with trinkets and memorabilia relating either to dogs (there are now “only” three, down from a family maximum of seven) and Liverpool FC, which his wife, the actor Hildegard Neil, supports. My visit is to talk to Blessed and his daughter Rosalind, also an actor, about two stage plays she has written, on which he is credited as “executive producer”.

“Ask me anything you want!” Blessed thunders, as we sit alone in his den, waiting, I have assumed, for the author. “Isn’t Rosalind going to be here?” I ask. “Oh, no no. No!” “I thought I was talking to both of you?” “Ah-ha. OK, I’ll go and find her.”

Luckily, she turns out to be in the garden, rather than her house seven miles away. The three of us are about to start speaking when Blessed announces that he must ask Hildegard to walk the dogs. He is absent for some time, Ros’s initial optimism about his early return giving way to visible doubts. She goes on a search mission, rounding up a contrite Blessed, who has been distracted by discussions with a gardener.

‘Ask me anything you want!’ … Blessed in his study. Photograph: Graeme Robertson/The Guardian

Ros’s plays, premiered at the Old Red Lion Theatre in London, cover such subjects as divorce, stalking, abusive relationships, eating disorders and self-harm. Not least because there is a character called Ros, audiences will inevitably wonder how much she made up. “I am divorced,” she says, “although the play isn’t the story of my marriage. However, I have experienced, in other relationships, mental and physical abuse. There was a guy a few years ago who had me up by my throat against a wall, smashed a mirror over my dog. I had to rush into the street, like in a horror movie.”

Survivors of domestic violence are increasingly encouraged to seek redress, however long after the events, by contacting the police or confronting the perpetrator. Has she thought of doing that? “No. No, I haven’t. All I can say is that I think I’ve spent so much of my life stuck in the past that I just don’t want to revisit those things any more. I found it hard to forgive myself for letting it happen over and over again.”

She found that writing The Delights of Dogs and the Problems of People, which features a dangerous relationship, “released a lot of that shame”. Thanks to a therapist and (after five years single) a fiance, she feels that “the cycle, I hope, is over”. Lullabies for the Lost, about a mental health therapy group, also reflects her experience: “Yeah. I’ve had mental health problems, I’ve had eating disorders, body dysmorphia, self-harm. I’ve fragmented myself into various characters.”

‘I fragmented myself into various characters’ … Rosalind Blessed and the cast of Lullabies for the Lost. Photograph: Adam Trigg

It strikes me that, for Blessed, the plays must have been like reading his daughter’s secret diaries. How much had he known? “Only a little because people lead their own lives. So it was deeply upsetting to read because you’re very protective of your children.”

The actor’s air of massive indomitability, exaggerated for professional effect, might lead some to suspect that he would be unlikely to pick up vulnerability in others, but he stresses that he has a side that is sensitive, even feminist: “My heroes – my heroines – are women. All my life, 90% of men have bored the arse off me. And it is women who have taught me everything.”

His support for the subject matter of his daughter’s plays also reflects a longer family history. His father, a coal-hewer in South Yorkshire, was crushed and gassed in an accident, leaving the family reliant on minimal sick pay. “My mother had a complete nervous breakdown,” he recalls. “I was 12. My dad was in hospital so I had to go along with my mother and sign forms for her to have electro-convulsive therapy.”

Blessed as Vultan in 1980’s Flash Gordon. Photograph: TCD/Prod.DB/Alamy Stock Photo

At the age of 18, while working on a building site before going to drama school, he had a breakdown of his own. His parents found their usually extrovert son staring silently at the fire, thrown by a local newspaper review that accused him of “overacting”. It’s a judgment that now seems funny given the scale of the performances that made him famous, but it devastated the young man. At a speech lesson in Rotherham, he collapsed into uncontrollable tears, then passed out. His teacher revived him by singing songs from Shakespeare, while stroking his head with a sponge.

“It was the only time in my life I’ve experienced a miracle,” Blessed says. “They stopped the storm in my head and cured me. But, in Yorkshire, they used to say of people, ‘That one’s got a tile missing.’ And all I can say is that, on that day, my tile was put back in place. But I feel I always have to make sure that the tile can’t come loose again.”

It never occurred to me when I was going through the wringer that I had a perfect ally in my dad Rosalind Blessed

How much did Ros know about her dad’s history? “I’ve always known about my grandmother’s breakdown. I didn’t know about Dad’s collapse until he wrote a book about his childhood called The Dynamite Kid. And it’s a strange thing, I now realise. Even though I knew that was in our family, it never occurred to me when I was going through the wringer that I had a perfect ally in my dad, who would have listened non-judgmentally. And I just didn’t do it. I suppose it’s a combination of shame and embarrassment and not wanting to upset people.”

A striking aspect of Ros’s writing is how freely her characters, male and female, use the C-word. As the obscenity often features in anecdotes from and about her father, is this a family trait? She laughs. “Yes, indeed. Growing up in our house, I didn’t even know the C-word was a bad word. In retrospect, it’s quite lucky that I wasn’t bandying it about at school. But I love swearing. I don’t see it as offensive. It’s like poetic seasoning in speech.”

In showbiz, the credit “executive producer” can signify significant creative input or a vanity courtesy. So in what way is Blessed executively producing Ros? “He’s doing it right now, frankly – publicising the shows. Dad came to an early reading of the plays and – because of everything we’ve discussed, the family history of mental illness – was very receptive to it. When I was younger, I distanced myself professionally from Dad because of accusations of nepotism. But I’m 44 now and I just wanted to get the plays out to anyone who might be suffering or struggling. I brought Dad on board so, quite frankly, we can afford to put it on, along with other financial backers. Also, if you want something to reach people’s ears, who better to shout than Brian Blessed?”

Ros writes in the plays about body dysmorphia. But, for Blessed, his size has been his fortune. Has he ever been uncomfortable about his body? “No, no. I love myself,” he bellows. “I do envy that,” his daughter responds.

‘Cats? Bears maybe!’ … Blessed in 1981, when he was in the stage musical Cats. Photograph: Rex/Shutterstock

“I love myself more than I love Rosalind – or my wife! I can’t wait to wake up in the morning and be me. I look in the bathroom mirror and I’m a cross between a yeti and a gorilla. But I love it. On mountains in the Himalayas, the sherpas call me Big Yeti. I love it that I’ve got a 55-inch chest.”

Ros looks thoughtful. “What’s interesting is that, despite having written the plays and been through therapy, I put on some weight last year because someone close to me was very ill, and I haven’t got rid of it yet. And so I start to think, as a size 16, maybe I shouldn’t be on stage, people probably shouldn’t have to look at me. And that’s ridiculous.”

Women in showbiz are notoriously pressured to lose weight, so has a producer or director ever waved a diet sheet or personal trainer at Blessed? “No! No never!” he says. Ros adds: “Isn’t that interesting?”

She has to leave for a dress rehearsal. I stay to ask him about Cats. In the 1981 stage premiere of the musical, Blessed played Bustopher Jones and Old Deuteronomy, roles taken by James Corden and Judi Dench in the new film version that has been critically clawed to box-office death. “I’ve not seen it yet,” he says. “I remember when my agent rang up and said, ‘They want to see you for a stage show called Cats.’ And I said, ‘Cats? Fucking gorillas maybe! Bears!’”

En route to the North Pole, I came across an igloo with an Inuit inside, playing Memory from Cats on a banjo. Now that is success! Brian Blessed

Whereas the movie was an expected success that became a disaster, the theatre version had the opposite journey. Blessed remembers the production team in tears of despair over funding, going with the composer Andrew Lloyd Webber to beg money from banks – who refused because the idea seemed so absurd. “But, when I went to the North Pole, I came across an igloo and there was an Inuit inside, playing Memory from Cats on a banjo. Now that is success!”

He insists that he feels “no jealousy or resentment about not being in the film. I will see it, but I worry. In the theatre, you can do anything – human beings as cats. But it’s harder on film. But I wish them well with it. I envy no other bugger. I celebrate talent.”

He is writing a travel book at the moment and hopes to play Prospero on stage, the insertion of a “very advanced pacemaker” having solved a cardiac arrhythmia problem that forced him to abandon his production of King Lear five years ago. He has always said his biggest ambition is to go into space, but surely he won’t now ever do it? “Of course I will! But it’s hush hush.”

The last two words are whispered – or at least reduce-boomed.

• Lullabies for the Lost and The Delights of Dogs and the Problems of People are at the Old Red Lion theatre, London, until 1 February.