Hughes cast himself, for the rest of his life, as the gatekeeper of Plath’s work: a snarling, sexy Cerberus. Permission to quote from Plath’s texts was next to impossible to secure, with the estate refusing the right if they disagreed with anything the author wrote; some Plath biographies from the time rely almost entirely on paraphrasing. Hughes made it clear in multiple letters to scholars and friends, some of which were published in newspapers at the time, that his was the definitive stance on Sylvia’s life and work. Moreover, sexy Cerberus had an affair with at least one Plath scholar, the British journalist Emma Tennant.
— What We Don’t Know About Sylvia Plath, Emily Van Duyne in Lit Hub