Gustav III was the first Swedish Protestant king to visit St. Peter’s in Rome. Desprez captured the visit in a watercolour. He then executed this oil painting in Sweden. Unlike in the watercolour scene, Gustav III is accompanied here by the Holy Roman Emperor Joseph II. He had indeed been present at St. Peter’s. The king also has a more central position, closer to Pope Pius VI, celebrating mass on the left. This emphasises the event’s significance.