Near the beginning of Ted Hughes: The Unauthorised Life, Jonathan Bate reports that he frequently found himself asking, “How can someone so good be so bad?” The scale and range of Hughes’s work have become apparent since the publication of his Collected Poems and Selected Letters, but Bate has read more of his unpublished work than any other scholar in the fraught lead-up to this book’s publication.

Previous biographers were guided by Hughes’s sister, Olwyn, but Bate mentions early on that she became “very angry” after reading a draft of an early chapter that discussed tensions among his upwardly mobile extended family. Bate also fell out with the estate (managed by Hughes’s widow, Carol) as he neared completion of his work, hence its subtitle. In such circumstances readers will expect revelations, and Bate is candid about many elements.

He identifies sources for Hughes's remarkable imaginative power as a compensating response to the family's move from wild west Yorkshire to industrial Mexborough and the departure to the second World War, and subsequent emigration to Australia, of his beloved elder brother Gerald. He was encouraged by his English teacher and matured by two years in national service, and the UK's "Butler" Education Act made a Cambridge degree possible for him. And at Cambridge he met Sylvia Plath, courtesy of another cultural initiative, the Fulbright Commission.

Bate is sceptical about Hughes’s much-mythologised switch from studying English to anthropology, and about his drunken first encounter with Plath. Here, and throughout, he depends on Hughes’s (previously unknown) journals, but he is careful to observe that “Hughes was good at covering his tracks and laying false scents” and “weeded” the archives.

There is no doubt, though, that Hughes’s encounter with the brilliant American changed his life. Each drove the other on with their encouraging example, and as they became each other’s subject a cycle of obsessive mythologising began. He was Heathcliff to her Cathy, and their seven years together colours every page of Bate’s book – as it has almost every other existing biography, film, novel and poem concerning Hughes.

Plath’s impact

Bate must also deal with the fact that Hughes spent 30 years trying to come to terms with Plath, in published work and in unpublished journals, in letters, in an unpublished 4,000-line precursor to Birthday Letters entitled Black Coat: Opus 131 and in another still-unpublished 46-section poem called Trial. The cataclysmic effects of Plath's suicide had the effect of sucking Hughes (and their children), and everyone who writes about them, back into those final weeks.

Bate clearly lays out a timeline that covers their time in the US and final year together. Coping with two young children in a foreign country and tense relations with in-laws added to the pressure on Plath. Their marriage could not survive a move to Devon when Hughes’s exceptional sales and London freelance life were taking off. In the wake of their split – after Plath witnessed Hughes kissing Assia Wevill in their Devon kitchen – Bate presents Hughes as a regular daytime visitor, helping out with the children and continuously talking to an understandably furious Plath.

Bate shows that Hughes’s guilt was exacerbated by the fact that he left his usual flat (and phone) on the night of Plath’s suicide, spending the night not with Wevill but with another lover, Susan Alliston, a secretary at Faber & Faber. Bate sympathetically fleshes out Hughes’s relationships with Alliston (who died young of Hodgkin’s lymphoma), and subsequent relationships with a Devon social worker, Brenda Hedden, and with his one-time babysitter Carol Orchard, although he is less sympathetic to Wevill, playing down Hughes’s mistreatment of her.

He also makes significant allegations about the centrality of Al Alvarez, the critic who helped to establish Hughes and Plath as harbingers of a new poetics and who may have been, Bate alleges, Plath’s final confidant and Wevill’s spurned lover.

Lothario v sadist

Serial unfaithfulness marks Bate’s account of Hughes’s life after Plath, which leads him up many garden paths, as when he writes that a memoir by Edna O’Brien “emphatically does not identify the lover as Hughes, but the rollercoaster she describes is a fine evocation of what an affair with Hughes would have been like”.

But Bate’s representation of Hughes as somehow exceptional is not quite true to the cultural whirl of 1960s and 1970s London, where contemporaries with tangled attachments included Harold Pinter, Kingsley Amis, VS Naipaul, Ian Hamilton and even his seeming opposite, Philip Larkin.

Lacking that context, Bate unconvincingly pictures Hughes as both a legendary Lothario and, in longer-term relationships, a charismatic “sadist”; uncertain about how to frame the “variations” of Hughes’s sex life, he repeats, without corroborating them, some troubling allegations.

Bate’s uncertainty about Hughes’s sexuality is mirrored in his treatment of his social climbing. Like Thackeray, Eliot, Evelyn Waugh, Betjeman and others, Hughes seems to have loved a lord, but only he is the subject of a “shrine” with “two stained-glass windows” in his honour at the prince of Wales’s country house.

Bate is exceedingly generous about these later affiliations even as his prose stumbles into gassy, chameleon comedy: “He relished the way that [the queen mother] was interested in everything and everybody, always positive in her outlook on the world . . . The exclusive Grimesta River on the island of Lewis became a Mecca for the Fisher King . . . Ted had come a long way,” and, a few pages later, “Ted struck up a friendship with [Pete Townshend] and they hung out at Soho House, an achingly trendy new private members’ club for arts and media types.”

Great biographies bring a comprehending latitude to bear on their subjects, seeing the life in relation to its creative legacy, and this is where Bate falters most. Hughes, Bate argues, was a Wordsworthian, a northern English autobiographer, who wanted instead to be a symbolist visionary like Coleridge.

For Bate, Hughes's two best books ignore Coleridge's siren example, the Wordsworthian childhood descriptions of Lupercal and, 40 years later, the account of a marriage in Birthday Letters. Everything between is presented as a detour or wrong turn, which certainly excludes some dated mythmongering poems, while handily allowing Bate to plot his book against what is probably the most famous literary love story and tragedy of the last century.

But there is a downside to cleaving so closely to Hughes's autobiographical poems. Almost nothing on the vivid, creaturely poems of Season Songs (1975) and Moortown Diary (1979), or the weird realism of Tales from Ovid (1997). Bate's treatment of the beauty and arresting strangeness of a book like River (1983) is typical, bogging that astonishing book down in an account – not uninteresting if you came across it in the annals of the Ted Hughes Society's west Devon chapter – of the book's genesis and sponsorship by British Gas.

As new archives become available – Bate moots publications of Hughes’s travel writing and the complete correspondence with Seamus Heaney – one inevitable consequence of this book is clear: further revelatory work, both biographical and critical, will follow.

John McAuliffe’s fourth book, The Way In, is published by the Gallery Press