‘More scandal is attached to the life of Ted Hughes than to that of any English poet since Lord Byron.” So judges biographer Jonathan Bate. Hughes’s marriage to Sylvia Plath is core to this. Her suicide in a bitter English winter, after Hughes left her for Assia Wevill, made him infamous.

When Hughes’s papers became available through the 2000s, Bate, a professor of English at Oxford, began writing a “literary life”. He wanted to study the genesis of Hughes’s ­remarkable poetry, avoiding cradle-to-grave ­biography and its controversies.

That proved impossible. Reading Hughes’s papers led Bate to conclude that “Sylvia Plath’s death was the central fact of Ted Hughes’s life. However he tried to get away from it, he could not; however the biographer broadens the picture, it is her image that returns … Plath remains the most vivid presence in his mental world.”

As the project shifted, necessarily, towards biography, Hughes’s estate stopped co-operating, and Bate’s (and Hughes’s) publisher, Faber, cancelled the book contract. Bate was limited to quoting the bare minimum of Hughes’s work. As I write, there is heated correspondence between the estate’s lawyers and the book’s publisher, HarperCollins.

Bate overcomes these limitations in a biography of exceptional power and lasting value. Ted Hughes: The Unauthorised Life is only the second Hughes biography, and the first to use the new archival material, including Hughes’s scattered private journals. Bate takes a measured but unflinching approach, neither apologist for Hughes nor moral critic. Rather, he presents facts drawn meticulously from the evidence and invites readers to make conclusions.

Bate brings balance to the often reductive Plath/Hughes mythology, doing service to both poets by showing them in complex detail. He ranges wider than Hughes’s first marriage, but the book centres on the argument that Hughes never stopped loving and mourning “Sylvia, the poetic other half of his youthful self”.

Hughes was a “poet of claws and cages”. His early work evokes the wilds of his native Yorkshire with visceral immediacy: the “hot stink of fox”, “woods crashing through darkness”. Bate depicts the youth that inspired them: roaming fields and ponds in search of hawk, owl, pike. Hughes’s deep connection to the land stayed for life, both in poetry and his conservation work.

Hughes met Plath at a 1956 Cambridge party to launch the poetry magazine Saint Botolph’s Review. She was an American Fulbright scholar, he a recent graduate. Bate weaves his excellent prose with Plath’s and Hughes’s recollections to draw a vivid picture of the famous night. There was jazz, “Luke Myers danced the ‘hot-wild jitterbug’ ”, “everybody was drunk”. “Shouting to be heard above the band and the crowd, Sylvia enthused to Ted about his poems”:

I was stamping and he was stamping … and then he kissed me bang smash on the mouth … I bit him long and hard on the cheek, and when we came out of the room, blood was running down his face.

Four months later, they married. Their short marriage was one of passion and close literary collaboration. “From 1956 until the summer of 1962,” Bate writes, “Ted Hughes and Sylvia Plath lived and worked together with utter loyalty and extreme intensity. They wrote joint letters to friends and families, they wrote poems and prose on the reverse sides of sheets filled with drafts of the others’ writing.” Each “became the other’s best critic”, achieving “synchronicity of vision through their shared imagination and observation, their conversation, their healthy competition, their daily and nightly bond of love and work”.

Bate captures their tenderness — Hughes bringing Plath “cold orange juice to quench sleep-thirst”, helping her fight “soul-battles”; Plath submitting Hughes’s poems, which led to the publication of his first book, The Hawk in the Rain. There were two years in the US, literary life in Devon, and children — Frieda and Nicholas. But the marriage broke down. Plath, a “manic-depressive genius”, flew into violent rages, burning Hughes’s work and books. He found the intensity of their shared life stifling and destructive to his writing: “the strain of living with her volatility was such that it was ‘her or me’. He would die if he stayed.”

Hughes began an affair with a friend, Wevill, and he and Plath parted. Seven months later, she died.

“When a marriage breaks down,” Bate writes, “the truth is usually somewhere between … two competing narratives”. That is augmented when one party dies — her cause adopted by third parties — and the other stays silent. “There have been many tellings of the last days of Sylvia Plath,” Bate writes. Using Hughes’s journals, he reveals Hughes’s version, showing that he visited Plath often in her last week to comfort her, distressed by the “volatility and unpredictability” of her mental illness: “Plans for reunion in one breath, demands for separation in the next.” Bate also identifies the woman Hughes spent Plath’s final night with: a girlfriend, Susan Alliston, not Wevill.

Hughes damned himself for Plath’s suicide. “She asked me for help, as she so often has. I was the only person who could have helped her, and the only person so jaded by her states and demands that I could not recognise when she really needed it.” Impossibly, it got worse: Wevill later gassed herself — as Sylvia had — killing her as well as Hughes’s four-year-old daughter Shura.

Hughes went on to a life of varied literary output — poetry, drama, translations, criticism, broadcasting and children’s books. He shielded Nicholas and Frieda from their mother’s increasing fame and the scandal surrounding her death, while diligently (but controversially) curating Plath’s literary legacy. And he juggled women, refusing, Bate shows, ever to commit wholly again. He scrabbled to earn money, lamenting constant interruption to his writing. When he was later appointed poet laureate, he used his platform to support ecological causes and enjoyed the excellent fishing that royal friendship afforded.

As Plath biographies and The Bell Jar solidified the “Plath narrative”, Hughes remained silent. Robin Morgan’s 1972 poem Arraignment accused him of rape and murder. Bate writes that the “Hughes name was vilified”. “Plathians” defaced Sylvia’s grave, chiselling “Hughes” off. Loath to fan publicity, Hughes “imposed upon himself a vow of silence that would endure for more than two decades: no published poems about Sylvia (unless sufficiently oblique …) ”.

Hughes, Bate reveals, believed he was “blocked”, poetically and psychologically, from Plath’s 1962 death until the 1998 publication of Birthday Letters — the searing poetry collection in dialogue with Plath’s, his story of their relationship, a love song to his dead wife.

It is hard to read: Hughes’s friend Seamus Heaney described it as “the psychic equivalent of ‘the bends’ ”. Hughes broke, there, from an impersonal poetics steeped in myth to the subjectivity of Plath’s confessional mode.

The acclaimed poems, Bate’s archival work shows, were no “late flowering”. They drew on nearly 30 years of drafts, journals, and publications that sought, obliquely, to work through his grief. Many more exist, unpublished.

The “price was high”. “Everything I have written since the nineteen sixties has been evading,” Hughes wrote. “If only I had done the equivalent 30 years ago, I might have had a more fruitful career — certainly a freer psychological life.” Birthday Letters brought Hughes “intense … liberation” and “catharsis”. He died less than a year after the book’s release. Bate’s biography is an exquisite tribute to Hughes’s memory, his poetry and grief.