Seymour began her literary career in 1975 with an historical novel,
The Stones of Maggiare. This was followed by six others concerned with Italy and Greece, including
Daughter of Darkness, about Lucrezia Borgia, and
Medea (1982). In 1982, Seymour turned to biography, beginning with a group portrait of
Henry James in his later years, entitled
A Ring of Conspirators. This was followed by biographies of
Lady Ottoline Morrell,(updated in 2024)
Mary Shelley and
Robert Graves, upon whom she also based a novel,
The Telling, and a radio play,
Sea Music. In 2001, she came across material on
Hellé Nice, a forgotten French Grand Prix racing driver of the 1930s and in 2004 published a book,
The Bugatti Queen, about Nice's ultimately tragic life. The book provided the material for an exhibition about Helle Nice on show until October 2025 at the Mac Museum at Singen, Germany.
The Bugatti Queen was followed by another life of an unconventional woman, that of 1930s film star,
Virginia Cherrill. This was also based on a substantial archive in private ownership, and published as ''Chaplin's Girl: The Lives and Loves of Virginia Cherrill'' in 2009. In 2002, Seymour published a book about herbs:
A Brief History of Thyme.
Noble Endeavours: Stories from England; Stories from Germany appeared in September 2013 from Simon & Schuster and was described as being a magnificent, deeply researched and scholarly work of 'unfazed optimism'. Seymour returned to biography with ''In Byron's Wake'' (2018) which covered the lives of
Lord Byron's wife and daughter,
Annabella Milbanke and
Ada Lovelace.
I Used to Live Here Once: The Haunted Life of Jean Rhys was published by Harper Collins in 2022. Seymour reviews and has written articles for newspapers and literary journals, including
The Economist,
The Times, the
Times Literary Supplement,
[the Financial Times, the Literary Review, and the
New York Review of Books. Formerly a Visiting Professor of English Studies at the University of Nottingham Trent, Seymour is a FRSL and FRSA and has served as a Royal Literary Fund Fellow at
King's College London. ==Personal life==