This drawing is an early sketch for one of the panels (most probably the right-hand panel) in Hughes's 1856 triptych The Eve of St Agnes (Tate Gallery N04604). The painting is based on Keats's poem of the same name. The finished design for the right- hand panel shows the lovers Madeline and Porphyro escaping from the castle. The scene shown by Hughes in this drawing does not appear in Keats's poem, and was presumably discarded by the artist because it departed from the text.
Several other sketches for the finished work are also in the Tate (Tate Gallery T06884, T06979).
Timothy Hilton, The Pre-Raphaelites, London 1970, pp.113-15
Leonard Roberts, introduction by Stephen Wildman, Arthur Hughes: His Life and Works, a Catalogue Raisonné, Woodbridge, Suffolk [to be published 1997]