This is an intriguing rarity. It bears a striking resemblance to the same artists' very rare first state of the Ilumination de la Croix de Saint-Pierre (of which Wollin lists only eight impressions, two hand-coloured). However, this etching offers a variation on the theme - the same subject, from the diametrically opposite angle. Giovanni Bernini's great canopied altar is seen from the North Transept, rather than the South, and the statue in the niche is of St Andrew, not St Longinus. Why the change? It may be an extremely rare trial proof, later rejected in favour of the better-known angle. Piranesi and Desprez may, on reflection, have preferred a viewpoint which was more familiar to their public, and which had more positive associations - the North Transept was the part of the church reserved for hearing confession, whereas the South was the site of daily masses. Regardless of their motives, this is an extraordinarily fine piece of work: the fluidity of the etched line, the rendering of architectural detail, and the atmospheric hand-colouring combine to do its magnificent subject justice. South, and not the North, Transept that the daily masses where held.