Who is Richard Sassoon from The Silent Woman: Sylvia Plath and Ted Hughes and what is their importance?

Richard Sassoon was one of Sylvia's gentleman friends. The couple was romantically invilved when she met her future husband, Ted Hughes. Although, Sylvia was deeply attached to Richard, his feelings for her lacked passion. She wrote a letter to her mother that said if she couldn't have Richard, she'd have to settle for another man since she didn't want to be a nun.