Scott's first work in Wales probably stemmed from a somewhat daring appointment by Lord Melbourne in 1840, when he selected an Englishman, Newell Connop Thirlwall, to be the new Bishop of St. David’s. St. David’s was the largest diocese in England and Wales, embracing all the old Welsh counties of Pembroke, Cardigan, Carmarthen and Brecknock, as well as most of Radnor, west Glamorgan, parts of Montgomery and Monmouth, and even contained eleven churches outside Wales, in Herefordshire. Thirwall visited every part of his huge diocese, inspecting schools and churches, supplemented out of his pocket the poorest parishes and their charities, and in his first year learnt Welsh. He also embarked on a programme of building or restoring Anglican churches throughout his diocese. This programme seems to have started in 1843 when he commissioned Scott and Moffatt to survey the church at Abergwili, next to his palace. Thirlwall probably heard about Scott through the publicity arising from his success in the competition for St. Giles, Camberwell, and he must have known Scott's cousin, John Scott of Hull, who was an undergraduate at Trinity when Thirlwall was the assistant tutor there, at the same time as Whewell and Peacock. By the time Thirlwall retired in 1874, he had completed 183 new churches or restorations, with work in hand for another thirty. Scott, however, made a rather modest contribution to this impressive programme.