From the article in The Independent:
Dr Mark Jacobs, a research fellow at Nottingham Trent University who has spent two decades studying 700 letters he received from Laura Riding Jackson as well as her literary works, said when she discovered the uncanny similarity in his texts she condemned her former lover as a "robber baron". ...
Dr Jacobs said Jackson accuses Graves of "robbing" her of key ideas which he appropriated as his own for his seminal study of poetic inspiration, The White Goddess, published in 1948.
He claimed that the inspiration for the work, which equates God with women, related to an early essay Jackson wrote in the 1930s called The Idea of God and her book, The Word Woman, which preceded Graves's magnum opus.