Her subjects have included Eglantyne Jebb; Krystyna Skarbek, aka Christine Granville; Hanna Reitsch and Melitta von Stauffenberg; and Elżbieta Zawacka.
She is an honorary patron of the Wimpole History Festival and lectures on the women of Special Operations Executive for the Andante group travel company Historical Trips.
[6] In 1919 Eglantyne Jebb was arrested in London's Trafalgar Square for distributing humanitarian leaflets, and few in England were sympathetic to a woman hoping to help the children of Britain's World War I enemies.
In 2012 Macmillan published Mulley's biography, The Spy Who Loved: the Secrets and Lives of Christine Granville, Britain's First Female Special Agent of World War II.
She made the first contact between the French resistance and the Italian partisans on opposite sides of the Alps in preparation for Allied invasion in the south, and secured the defection of a German garrison on a strategic pass in the mountains.
Mulley's The Women Who Flew for Hitler was published by Macmillan in the UK, and St Martin's Press in the US, in 2017, and subsequently in Poland, Finland, the Czech Republic, and China.
Yet although both were motivated by deeply held convictions about honour and patriotism, their contrasting views on the Nazi regime meant they ended their lives on opposites sides of history.
"Vividly drawn... this is a thrilling story", wrote Anne Sebba in The Telegraph,[12] while The Times called the book "popular history of a high order",[13] and The Spectator thought it "well researched and beautifully written".