A new, unauthorised biography of Ted Hughes retraces what happened in the days leading up to Sylvia Plath’s suicide in 1963.

According to a biography of Hughes by Sir Jonathan Bate, provost of Worcester College, Oxford, who had “full access, unlike earlier biographers” to the poet’s archives in the US, as well as to material held by the British Library, a poem by Hughes called ‘Last Letter’ was inspired by an argument Hughes and Plath had on the weekend of her death.

The Sunday Times says that Bate writes in the new biography that on the Friday morning of that weekend, Plath sent an “enigmatic parting letter” to Hughes saying that she planned to leave the country and never see him again. She had assumed that the letter would not reach her estranged husband until Saturday but owing to a speedy second post it arrived that afternoon. Hughes rushed to Plath’s home in Primrose Hill, north London. Plath is said to have seized the letter from Hughes and burned it.

Bate also said that on the following day, Saturday, Plath rang Hughes only to find his lover, Susan Alliston, answering the phone. The book also contains information about Hughes’s relationship with Assia Wevill, who killed herself in 1969, leaving a note that stated the couple could not live together “because of the memory of Sylvia”.

Last year the estate of Ted Hughes hit back at claims that it had barred Bate from archives, asked that he return photocopies of privately held documents, and withdrawn his right to quote extensively from the poet's work – described by the professor as "an essential aspect of serious scholarship".

In reply, Damon Parker, spokesman and solicitor for the Ted Hughes estate, said: "Concerns were expressed to Professor Bate as early as 2010 that he might be straying from the remit agreed for his book. He repeatedly resisted all requests to see some of his work in progress, as agreed. His comments to the press in recent days have confirmed the concerns that the estate had long held."

As a result Bate was unable to continue his planned “literary life” of Hughes after Hughes’s widow, Carol, withdrew her support for the book. The unauthorised biography is being published by William Collins.

Background: More twists in the biography tale