Nothing is more likely to inspire us to see for ourselves than a warning about the effects of looking. Take the media interest this month when it was revealed that the British Museum's exhibition, Life and Death in Pompeii and Herculaneum, is to include a "parental guidance" notice. The reason? An ancient marble sculpture of the god Pan (a part-human, part-goat figure) having sex with a she-goat is not to be segregated, as it has been since its discovery in 1752, but displayed openly with the other exhibits – a liberal move by London, if also one which dulls the object's impact. Getting this story into the news ensures that centuries of censorship are not swept under the carpet, and that Pan, and the show he speaks for, remain "hot property".

But the news story also exaggerates this censorship. Far from being forgotten in its first modern home in the royal palace at Portici on the Bay of Naples, the sculpture, which was part of a restricted collection in the cellars, was quickly a celebrity.

The German art historian Johann Joachim Winckelmann, who visited the palace four times between 1758 and 1767, thought better of being "the first to apply" for a viewing licence, and called the Englishmen who claimed to have seen the piece liars. But by 1794 another Englishman is insistent: he writes that he has seen the sculpture, but that it is too indecent to describe, deserving to be thrown into the volcano. Luckily no one listened, and in the 19th century the sculpture was transferred to its new home, now the National Archaeological Museum of Naples, where it again became part of a reserved collection....