The collection has always been in the possession of the Paul Mellon Centre for Studies in British Art (or its predecessor institution, the Paul Mellon Foundation). Image source: Peter W. Beckhaub, “Tawny", The 6th Duke Of Devonshire's Spaniel",” 1819. Accessed via https://photoarchive.paul-mellon-centre.ac.uk/objects/491935/tawny-the-6th-duke-of-devonshires-spaniel.