Horne was an architect, art collector and art historian. In the early 1880s he began working for A. H. Mackmurdo, an intellectual architect with strong social concerns and in the mid-1880s they went into partnership. He was involved with the Century Guild, a loose association of architects, designers, and craftsmen set up by Mackmurdo. His collection included a number of Wilson drawings, notably:
D68 Still-Life with Flask, The British Museum;
D69 Chair and Sword Hilt, National Galleries of Scotland;
D75 Landscape Sketch: View through the Arches, National Galleries of Scotland;
D119 The Castle of Sant' Angelo, Rome, Ashmolean Museum, University of Oxford;
D180 A Roman Aqueduct, National Galleries of Scotland;
D181 The Torre del Fiscale near Rome, National Galleries of Scotland
D265 Study of Foliage, National Galleries of Scotland;
D274 Temple of Bacchus, Rome, Ashmolean Museum, University of Oxford;
D278 Landscape Composition - An Italian Garden, National Galleries of Scotland;
D370 Conway Castle, The National Library of Wales, Aberystwyth / Llyfrgell Genedlaethol Cymru.
