This study reconstructs Brittain's feminist theory, which mainly refutes assumptions made about women, supports companionate marriage, and demands the communal reorganization of child care and domestic work to enable a married woman to work outside her home. It compares her theory to her five novels. Doing so, it uncovers revealing feminist 'flaws', above all that marriage remains, the sine qua non for a woman's happiness. The study describes Brittain's way to the top as a formidable obstacle race, in which she constantly had to fight the men she loved, her children, her parents, and resulting domesticity in order to find time to write 'the book of the decade'. She reached her goal with the publication of Testament of Youth in 1933.