Complex sentence: The painting was based on a photograph of Mann by Charles Thomson and was originally intended to promote the Stuckists "Real Turner Prize Show 2003": at that time the placard contained the text, "Serota needs a good spanking".
Split into simpler sentences: The painting was based on a photograph of Mann by Charles Thomson and was originally intended to promote the Stuckists "Real Turner Prize Show 2003". At that time the placard contained the text, "Serota needs a good spanking".