This watercolour is based on an etching by Giovanni Battista Piranesi (1720–78) that was titled Carcere Oscura con Antenna per Suplizio de’ Malfatori (Dark Prison with a Courtyard for the Punishment of Criminals) and published in 1743 (see the source image above). The drawing is larger than the original etching – unlike a second version, which is exactly the same size (see figure 1) – but otherwise it follows the composition reasonably closely, replicating the figures, and many of the architectural details and the distribution of light. Overlaying images of the watercolour with the Piranesi print highlights the changes made by Girtin and there is no question of the artist having traced or slavishly copied the original. Thus details such as the chain suspended from the pulley to the left are omitted, whilst Girtin’s drawing significantly expands the composition laterally to create a less claustrophobic effect. The watercolour comes from the collection of one of Girtin’s most important early patrons, John Henderson (1764–1843), and, along with works such as The Temple of Augustus at Pula in Istria (TG0886) and Rome: The Capitol from the South East (TG0891), it appears to bear out the testimony of the early biographer of Joseph Mallord William Turner (1775–1851), Walter Thornbury (1828–76), that Girtin ‘studied … and copied’ Piranesi’s prints at Henderson’s home at the Adelphi in London (Thornbury, 1862, vol.1, p.87). Nonetheless, there has been some question about the attribution of the work; Thomas Girtin (1874–1960) and David Loshak did not include it in their catalogue (Girtin and Loshak, 1954), whilst Tom Girtin (1913–94) thought that it was executed by Henderson (Girtin Archive, 14). This too was my opinion when I first examined the drawing; the poor anatomy in the figures and the unconvincing perspective that results from the opening out of the space to the right of the composition suggested the work of an amateur. However, a growing familiarity with Girtin’s copies after prints has helped to changed my thoughts, and I would point to the careful articulation of space through the subtle manipulation of light as being beyond the capabilities of Henderson. On balance, I now think that the work is by Girtin himself.