Sometime heir to the English throne, courtier in danger of losing her head, spy-mistress and would-be architect of a united Catholic Britain: Lady Margaret Douglas is the Tudor who survived and triumphed — but at a terrible cost.

Niece to Henry VIII and half-sister to James V of Scotland, the beautiful and Catholic Margaret held a unique position in the English court. Throughout her life, she was to navigate treacherous waters: survival demanded it. Yet Margaret was no passive pawn. As the Protestant Reformations unfolded across the British Isles, she had ambitions of her own: to see her family rule a united, Catholic Britain.

Drawing on previously unexamined archival sources, So High a Blood tells the story of how an unworldly girl, summoned to a glittering, dangerous court, transformed herself into a powerful, political noblewoman who helped shape the history of Britain in the sixteenth century.