In 1979, Ridley was appointed a lecturer in history at the
University of Buckingham, where she was promoted to Senior Lecturer in 1994, to Reader in 2002, to Senior Tutor responsible for student discipline the next year, and finally to Professor in 2007. At Buckingham she continues to serve as Senior Tutor and to teach history and has been in charge of the university's Master of Arts course in biography since establishing it in 1996. Ridley's first book was
The Letters of Edwin Lutyens (1985), a collection of her great-grandfather's letters, edited jointly with her mother, Clayre Percy. She combined
social history with her sport of
fox hunting to produce
Fox hunting: a history (1990), which begins with the words "Fox hunting isn't strictly necessary." In 1995, Ridley's
The Young Disraeli was published, dealing with
Benjamin Disraeli's early years. She disputes that he should be considered the father of
one-nation conservatism, writing that "Disraeli didn't use the expression and nor did he want to create a classless society... The legend of Disraeli was created largely by the Conservative party, which needed a hero on whom to pin its ideas about making the party electable in a democracy." Ridley's biography of her great-grandfather Edwin Lutyens,
The Architect and his Wife, won the Duff Cooper Prize for 2002. In 2008, Ridley was given a
Leverhulme Research Fellowship to work on her biography of
King Edward VII, ==Personal life==