This thesis offers the first complete study of the English domestic architectural projects of John Montagu, 2nd Duke of Montagu (1690-1749). Montagu held key offices at court and in the military as Master of the Great Wardrobe (1709-49) and Master-General of the Board of Ordnance (1740-42, 1742-49), and was an important patron of learned societies, Huguenots, the arts and Freemasonry. This thesis examines Montagu’s newly-accessible private archives, institutional records and papers found in local record societies, as well as studying all surviving building fabric. The thesis establishes the nature of Montagu’s domestic architectural output, addresses issues of patronage, the extent of his personal involvement in the design process, and the working methods to execute his vision. It analyses themes that emerge across his building projects, including his pragmatism and ideas relating to medievalism. His interest in Gothic Revival and antiquarian study is examined as part of his mission to revive seigneurial rights and establish his comparatively new dynasty amongst Britain’s leading nobility. I argue that his use of heraldry and architectural salvage to create his schemes was a particular and characteristic manifestation of these ideas. The impact of his Huguenot education, professional positions and financial circumstances on his architecture are considered. I establish his long working relationship with the architect Henry Flitcroft (1697-1769) and the significance of his patronage of surveyors and cartographers in relation to his estates and architecture are addressed. By situating Montagu as an important but hitherto largely overlooked figure of the first half of eighteenth-century Britain, I argue that the scale and nature of his architectural work and patronage make him a significant figure in the architectural landscape of the period. By considering his dynastic ambition and seigneurial revival programme as a central part of his motivations for the creation of his medievalist schemes, this thesis contributes to current debates over the meaning and motivations for the Gothic Revival in eighteenth-century England.