One of the most beautiful and brilliant women of her time, Gladys Deacon dazzled and puzzled the glittering social circles in which she moved. Born in Paris to American parents in 1881, Gladys emerged from a traumatic childhood - her father having shot her mother's lover dead when Gladys was only eleven - to captivate and inspire some of the greatest literary and artistic names of the Belle Epoque. Marcel Proust wrote of her, 'I never saw a girl with such beauty, such magnificent intelligence, such goodness and charm.' Berenson considered marrying her, Rodin and Monet befriended her, Boldini painted her and Epstein sculpted her. She inspired love from diverse Dukes and Princes, and the interest of women such as the Comtesse Greffulhe and Gertrude Stein. In 1921, when Gladys was forty, she achieved the wish she had held since the age of fourteen to marry the 9th Duke of Marlborough, then freshly divorced from fellow American Consuelo Vanderbilt. Gladys's circle now included Lady Ottoline Morrell, Lytton Strachey and Winston Churchill, who described her as 'a strange, glittering being'. But life at Blenheim was not a success: when the Duke evicted her in 1933, the only remaining signs of Gladys were two sphinxes bearing her features on the west terraces and mysterious blue eyes in the grand portico. She became a recluse, and the wax injections she'd had to straighten her nose when she was 22 had by now ravaged her beauty. Gladys was to spend her last years in the psycho-geriatric ward of a mental hospital, where she was discovered by a young Hugo Vickers. Intrigued and compelled to unmask the truth of her mysterious life, Vickers visited her over the course of two years, eventually publishing Gladys, Duchess of Marlborough, a biography of her life - and his first book - in 1979, two years after Gladys's death. Forty years on, Vickers has now completely rewritten and revised his original biography, updating it with previously unavailable material and drawing on his own personal research all over Europe and America. He once asked Gladys, 'Where is Gladys Deacon?' She answered him slowly, 'Gladys Deacon? . . . She never existed.' The Sphinx is a fascinating portrait of this elusive but brilliant woman who was at the centre of a now bygone era of wealth and privilege - and a tribute to one of the brightest stars of her age.