Turner filled the upper half of this page with studies of the castle at Brest. Tate curator Ian Warrell has suggested that Turner used this sketch when devising an unfinished oil painting in the Turner Bequest; see Tate N05514.1 Brest features on multiple pages in this part of the volume, a list of which is included in the sketchbook introduction.
Ian Warrell, Turner on the Loire, exhibition catalogue, Tate Gallery, London 1997, p.231; Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Haven and London 1984, p.528 no.527, pl. 511.