Ted Hughes 'was in bed with lover' when Sylvia Plath died

Poet Ted Hughes was in bed with another woman on the night his first wife Sylvia Plath killed herself in 1963, according to a new biography.

Sir Jonathan Bate, provost of Worcester College, Oxford, used new evidence - including Hughes' lover's diary - to piece together Plath's final weekend.

He had "full access, unlike earlier biographers" to Hughes's archives in the US and used British Library papers.

The book also reveals Plath sent Hughes an "enigmatic parting letter".

It stated that she told Hughes she planned to leave the UK and never see him again, with the letter arriving two days before her death on the Friday afternoon, The Sunday Times reports.

According to the biography, Plath - who had been estranged from Hughes for six months - had assumed it would not reach him until the Saturday, however it arrived early because of a speedy second post.

A concerned Hughes then rushed to Plath's home in Primrose Hill with the letter, which she snatched away and burnt.

"This was their final face-to-face which Ted turned into [his poem] Last Letter, which was only published in 2010," said Sir Jonathan, adding: "This explains that poem."

Last Letter begins with the line: "What happened that night? Your final night?" It ends with the moment Hughes is informed of Plath's death: "Then a voice like a selected weapon or a measured injection, coolly delivered its four words deep into my ear: 'Your wife is dead'."

The biography claims Plath rang Hughes the next day but his lover Susan Alliston answered. According to Alliston's previously unseen diary, she then handed the receiver to Hughes, who told Plath "take it easy, Sylvie".

Hughes was with Alliston at a friend's flat in Bloomsbury on the Sunday when The Bell Jar author killed herself, according to Sir Jonathan, who also claims they were together when Hughes heard of Plath's death the next day.

Other revelations in the biography concern a love triangle Hughes was caught up in five years later, involving Assia Wevill, who killed herself in 1969, Brenda Hedon and trainee nurse Carol Orchard, who was 20 at the time.

Hughes "could not decide" according to Sir Jonathan, who quotes a journal belonging to Hughes in which he called the women "A, B and C".

Hughes wrote: "Three beautiful women - all in love, and a separate life of joy visible with each, all possessed but own soul lost."

He then wrote a poem about his dilemma, which began: "Which bed? Which bride? Which breast's comfort."

Hughes eventually wed Orchard in 1970 and they were married until his death in 1998. She withdrew her support from the biography in 2013 over a dispute.

The book features several other women who claim to have had relationships with Hughes who are speaking for the first time, including his first serious girlfriend, Shirley, from his university days at Cambridge.

Sir Jonathan concludes that Plath's death at the age of 30, and Hughes' subsequent guilt, were "central" to the rest of his life.

"However hard he attempted to get away from it, he never could," he wrote.

Last week the book, Ted Hughes: The Unauthorised Life by Jonathan Bate, was one of 12 works of non-fiction to be longlisted for the Samuel Johnson Prize.