In August 2014, Mould was one of 200 public figures who were signatories to a letter to "The Guardian" opposing Scottish independence in the run-up to September's referendum on that issue. In October 2015, Mould appeared on BBC's "Gardeners' World", in the garden of his home, discussing his passion for nature and talked of his interest in varieties of rose which would have been grown in the time of Sir Anthony van Dyck. He also discussed the work of one of his favourite artists, Cedric Morris, who was also a great plantsman. Mould is a keen collector of Morris's work (for his private collection), and champions modern British artists in general; he cites the Bloomsbury Group amongst his favourites.