For over two centuries St Stephen's Chapel in Westminster was been pivotal to the interpretation of 13th-14th century Gothic architecture. First constructed during the twelfth century, extensively redecorated under King Henry III (1227-53) and entirely rebuilt under Edwards I-III (1292-1363), this lavishly decorated palace chapel was located at the centre of power and devotional activity for England's Plantagenet rulers. Demolished in 1834 after centuries of re-use as the House of Commons, the building is known only through antiquarian drawings and prints. Architectural historians have long considered St Stephen's to be a pioneering design, identifying innovative features which revolutionised architectural practice and set the pace of development for the English Decorated and Perpendicular styles. Yet despite the building's fundamental importance to the history of medieval architecture, a dedicated monograph re-assessing its appearance, construction history and the political context of its creation is long overdue.