Miranda Seymour was two years old when her parents moved into Thrumpton Hall, the family's ancestral home in Nottinghamshire. This celebrated Jacobean mansion is on the south bank of the River Trent at the secluded village of Thrumpton. A Fellow of the Royal Society of Literature and in recent years a visiting Professor of English Studies at the Nottingham Trent University, Seymour is also a Fellow of the Royal Society of Arts. She is an alumna of Bedford College, London, now part of Royal Holloway, University of London (BA English, 1981).
In 1972 Seymour married the novelist and historian Andrew Sinclair and had a son, Merlin. Her second marriage, to Anthony Gottlieb, then executive editor of The Economist and author of a history of Western philosophy, ended in 2003. A transatlantic literary room-swap led to her third marriage, in 2006, to Ted Lynch, a Bostonian. Seymour divides her time between London and Thrumpton Hall, now used both as a family home and for weddings and corporate events.
Biographies by Seymour include lives of Lady Ottoline Morrell, Mary Shelley, Robert Graves (about whom she also wrote a novel, The Telling and a radio play, Sea Music) and a group portrait of Henry James during his later years (A Ring of Conspirators). In 2001, she came across material on Hellé Nice, a glamorous, long-forgotten French Grand Prix racing driver from the 1930s. After extensive research on a well-buried subject, Seymour published a highly acclaimed book in 2004 about Hellé Nice's extraordinary and ultimately tragic life. In 2008 she published In My Father's House: Elegy for an Obsessive Love (Simon & Schuster, UK). The same book was published in the US as Thrumpton Hall (HarperCollins) and won the 2008 Pen Ackerley Prize for Memoir of the Year. Always attracted by unusual and challenging subjects, Seymour wrote about the life of a charismatic 1930s film star, Virginia Cherrill, based upon a substantial archive in private ownership. Noble Endeavours: Stories from England; Stories from Germany was published in September 2013 by Simon & Schuster. Seymour's 2018 book, In Byron's Wake, celebrates the lives of Lord Byron's wife and daughter – Annabella Milbanke and Ada Lovelace.