Mary Grey was the youngest sister of Lady Jane Grey and a possible claimant in the Tudor succession. Like her sister Katherine, her marriage choices and royal blood made her vulnerable under Elizabeth I.
In 1565 Mary secretly married Thomas Keyes, Elizabeth I’s sergeant porter, without the queen’s permission. Because Mary stood within the Tudor succession, Elizabeth treated the marriage as a political offence: Keyes was imprisoned in the Fleet and Mary was kept under house arrest in a succession of households. The couple were never allowed to resume married life before Keyes’s death in 1571. Mary eventually obtained greater freedom but remained childless, dying in 1578 and receiving burial in Westminster Abbey.
Elizabeth Fremantle’s Sisters of Treason follows Mary Grey and her sister Katherine after Jane Grey’s execution, when their Tudor blood makes ordinary marriage and motherhood politically dangerous under Mary I and Elizabeth I. Philippa Gregory’s The Last Tudor gives Mary her own final section, emphasising the determination of the physically small youngest sister to claim a private life despite surveillance and imprisonment. Leanda de Lisle’s The Sisters Who Would Be Queen reconstructs the historical Mary alongside Jane and Katherine, showing how secret marriages and disputed succession rights kept all three sisters within the monarchy’s field of suspicion.