The sketch book (Pls 6-11) in which François-Joseph Bélanger made his observations while in England is a fascinating document of inter-cultural exchange; and, in a number of cases, records vanished buildings of whose appearance we are now ignorant. The sketch book (in the École des Beaux Arts, Paris) has not hitherto been the subject of a detailed analysis. It was referred to by Jean Stern in his biography, À I’Ombre de Sophie Arnould: François-Joseph Bélanger (Paris, 1930), where he hazards a guess that it belongs to a visit Bélanger may have made as a very young man, when he left the École de l’Académie Royale d’Architecture in 1766. He could certainly have had introductions from his master David Leroy, who had known and corresponded with William Chambers since their student days. Chambers was then well established in practice as an architect, although not yet Comptroller of the Works. He was the obvious person to whom the master would send a promising student anxious to study the latest trends of architecture in England. However, a cursory glance at Bélanger’s sketches shows that some of them at any rate belong to a later date; for instance Adam’s designs for Pulteney Bridge at Bath (fol. 116) were not made until 1768, and the bridge was not completed until 1774; the water-wheel at Painshill (fol. 78) was not installed until 1772; and the elevation of a villa (fol. 96, Pl. 17b), inscribed ‘Cobham M. Hamilton’, is evidently the design by Richard Jupp exhibited in the Royal Academy of 1778, which, although possibly made for Hamilton, was almost certainly built after he had sold Painshill to Benjamin Bond Hopkins in 1773. What therefore are we to make of Bélanger’s sketch book? Does it cover several visits? What does it tell us of his interests, and how do these relate to his activities in France?