The Sphinx: the Life of Gladys Deacon — Duchess of Marlborough by Hugo Vickers - review | London Evening Standard

A trip to Blenheim Palace offered tantalising tidbits, but it wasn’t until 1975 that Vickers discovered Gladys, aged 94, locked away in a psychiatric hospital in Northampton. He managed to gain access, with a view to writing her life. “I don’t see why I should be disturbed by Mr Vickers,” the duchess snapped. But he soon earned her trust, and paid 65 visits before her death in 1977, gathering hours of first-hand accounts for his biography, first published in 1979.