Eruption of Souffrier

 was a painting by Turner which the Rani once had copied on a room-divider screen hiding her TARDIS. As the name suggests, it was a portrait of a volcano erupting. Were an unauthorised person to approach, mustard gas would spew out of the top of the painted volcano. The Sixth Doctor thought it an odd choice for the Rani, because it was "too passionate for the Rani's sterile tastes".

Apparently finding the lack of eruption a curious anomaly, he sought out the secrets of the painting. Affixing a string to the top of the volcano, he and Peri stood back from the painting while he gave it a gentle tug. This tripped the Rani's trap, and the volcano erupted, momentarily incapacitating the time travellers with its deadly gas. (TV: The Mark of the Rani; PROSE: The Mark of the Rani)

Behind the scenes
The painting is never named in the serial, but the novelisation claims: "Painted in the style of Turner's , it portrayed, in sultry ambers and vivid scarlets, a smouldering volcano". The difficulty is that neither that description nor the image which shows up in the serial is reminiscent of . That painting is much darker, and notably bereft of "sultry ambers and vivid scarlet". Art lovers watching The Mark of the Rani without the benefit of the novelisation could easily believe they were looking at an attempted replica of Turner's other notable volcanic work, Eruption of Vesuvius.

If the Bakers are to be believed and it is of the Souffrier explosion, then the full name of the painting in the real world is The Eruption of the Souffrier Mountains in the Island of St. Vincent, at Midnight, on the 30th April 1812, from a Sketch Taken at the Time by Hugh P. Keane, Esquire.