The Catastrophic Repairs of Holyrood Abbey Church in 1760

The collapse of the significant church of Holyrood Abbey in Edinburgh in December 1768 is discussed as the result of the ill-conceived repair of the roof in 1760, i.e., the substitution of the timber trusses with closelyspaced diaphragm masonry walls that aggravated the delicate equilibrium of the vaults and the poor state of a building being mutilated over 250 years. This study interprets these repairs by demonstrating the authorship and partnership of the architect John Douglas with the mason-developer James McPherson, who combined architectural ambition (the aesthetics of a flagstone roof) with the (cheaper) option of diaphragms, which would not involve a wright. The detailed examination of the procurement, the process of the intervention, the collapse, and the limited impact of its aftermath, are framed in a wider technical and historical context in Edinburgh and Scotland, during a period marked by several failures of medieval churches, and reveals a poor understanding of a critical element in Gothic construction. Analysis of all public archive material available sheds light on key events of the case, and critical study of the work of the two partners’ attempts to identify the intentions of their project, whose limitations were inevitable once the partnership was formed.