‘Sinéad, you must read my diaries. The most naked ones are in Emory College, Georgia.”

This was a voicenote left for me by Edna O’Brien in 2023, after I had started to film a feature documentary with her, granting me access to the most personal work she created in her lifetime: her unpublished diaries.

She had been initially reluctant to help me make the film. She was 92 and had cancer, so her time was limited. But she became more enthused after I showed her an old TV clip of herself in her 40s, with her parents.

The entire Edna mythos was within that clip. Her mother claims that O’Brien’s books had never been an issue at home while her father is playing the role of the jovial Irishman. In reality he was a violent alcoholic and she was disgusted by her daughter’s writing. The British interviewer, oblivious, is delighted when her father starts to sing Danny Boy.

“I look worried and terrified,” she said when I showed her the video.

She was hospitalised after that encounter but her interest was piqued and we began to talk more. She would record long voice memos via our executive producer, Barbara Broccoli, who was caring for her. One day, I received the message that O’Brien wanted me to read her diaries. They did not disappoint.

She had led one of the great lives of the 20th century and everything was there: the early attempts at writing, her doomed marriage to Ernest Gébler, the publication of The Country Girls, love affairs with a litany of bad men, her complex family relationships, many dreams and many parties, alongside long and beautiful observations of nature.

One extraordinary feature of the diaries, which are read by actor Jessie Buckley in the film, was the annotations that appeared below some of the earlier entries. They were often vicious commentaries and I suspected these were by Gébler (which was then confirmed to me by O’Brien and Gébler’s son, who recognised his father’s handwriting).

At times, I feared that the author’s personal life and diaries were so colourful that they might distract from her literary achievements – as so often happens with female artists. In the end, my strategy in making the film was to attend to both sides of her.

Here are five excerpts from the diaries that helped me tell those two parts of O’Brien’s story: the glamour and the doomed love, but also her intellectual abilities, the quality of her writing and its context – and what a thing it was to have created this work from such difficult circumstances.

***

Prurient = itching with lewd desire.

Winnow = separate.

Ingenuousness = artlessness.

This early entry shows O’Brien’s desire to teach herself a better vocabulary. The only books in her home were her mother’s prayer books and her horse-obsessed father’s bloodstock manuals.

The novelist was born in 1930 in County Clare soon after the ending of British rule. Ireland was floundering; locked in the economic war of the 1930s with Britain which had placed revenge tariffs on Irish goods after independence. Responsibility for health and education was outsourced to the highly patriarchal Catholic church.

Language fascinated O’Brien, but her formal education was cut short when she was sent to train as a pharmacist in Dublin while in her teens. There she met Gébler, a successful writer who had written The Plymouth Adventure. His circle mocked her wide-eyed enthusiasms. This entry is from that era.

I love that she continued to improve herself despite the snideness.

***

Carlos full of expressions and sweetness, went to Ennis, mostly tea, prepared to return, Ernie thinking more and more of himself.

[annotation] Ernie fed up with her aunties, with her crude narrow-eyed Catholic disapproving tribe of six-toed trolls. They hate E.

At first I was confused by these annotations. Could Gébler have been so malicious and would he have referred to himself in third the person? Very much yes, his son confirmed.

This 1958 entry follows a visit to O’Brien’s parents. The couple moved to London shortly after but O’Brien was overcome with homesickness and wrote The Country Girls in weeks. This coming of age story set in County Clare won great acclaim for its frank and funny depictions of toxic best friends and terrible men, but many Irish people were mortified. It was banned, as were her next five books. One woman told me that as a child, she was instructed by her mother to burn The Country Girls in their back garden.

***

Began second novel calling it The Lonely Woman.

Ernie having sketched it out in detail and in time he would correct the manuscript equals re-write it.

O’Brien’s success enraged Gébler and he began to believe he had written her books. She had to give her royalties to him in return for an allowance. Eventually she left.

After a bitter custody battle, he returned to Ireland. Though O’Brien would write many great books after leaving him, he waged a whispering campaign against her for the rest of his life.

He would also intercept her correspondence and pretend to be her agent to stop producers from adapting her work. Instead he recommended they approach the very talented Ernest Gébler.

***

Despite everything, I am well and happy and free in a way I have never been before.

The 1960s were a thrilling time for O’Brien after the tumult of her divorce. She hosted glamorous parties and socialised with Princess Margaret and Paul McCartney. Admirers included Richard Burton, Robert Mitchum and Marlon Brando. Her success enabled her to buy a townhouse on Carlyle Square in Chelsea.

Alongside this, she was publishing hit books almost every year, an exceptional run that continued until 1970. In Ireland she was mocked for her success and she struggled with her feelings about her family and the abuse she had experienced as a child.

She began seeing the controversial psychiatrist, RD Laing. In 1970 they took LSD together, an experience O’Brien described as “terrifying.”

***

Said he wanted total detachment and total intensity. Wanted me to have several lovers and none. At the end of a fairly hostile copulation said I was just too powerful that he was just a bit of elastic that did not know when he was going to snap.

O’Brien’s propensity for difficult men continued. In the late 1970s she began an affair with a senior married British politician whom she nicknamed “Lochinvar”. There were heady assignations in the House of Commons but he would not leave his wife and she could not let go.

The scale of her obsession is hard to overstate. She stops writing fiction and devotes thousands of diary pages to her feelings of guilt and longing for his “lovely honey-coloured body”. Friends and even doctors implore her to give him up.

The lack of income forced her sell her Chelsea townhouse for £235,000. Within five years it was worth £5m. She would live as a tenant for the rest of her life. Her next books didn’t sell and she came close to suicide.

***

O’Brien once said to me, “I used to think love mattered most to me. It doesn’t. I ask myself now about wars and famines and cruelty and God. I do not believe in God in the same way. I do not.”

Her interest in politics had been constant – she had once stood bail for IRA volunteer Dolours Price but her later work, beginning with The House of Splendid Isolation in 1994, made this more overt.

Controversy continued but her literary spark had returned: her 2015 novel The Little Red Chairs is considered to be one of her best books.

It was a wonderful act of resilience and renewal. O’Brien would continue to write until her death at the age of 93.

• Blue Road: The Edna O’Brien Story is released in UK cinemas on 18 April