The picture, entitled Rosie, is of a girl wearing a dress but no underwear sitting on a pew. The decision of the Hayward Gallery not to show it was taken after advice from the police, who explained that the climate surrounding images of children's has changed since 1976.
The forthcoming exhibition has already toured places as diverse as Israel and New Zealand, so we might ask if this anxiety is peculiarly British. Predictably, the photograph has already been condemned as "utterly horrific " and as "child pornography" by Esther Rantzen, though when exactly Ms Rantzen saw this particular image is difficult to ascertain. One can't help wondering if this photo had been taken by anyone other than Mapplethorpe whether it would have been withdrawn. Unusually for a Mapplethorpe work the obscenity here is largely in the eye of the beholder.
While much of Mapplethorpe's oeuvre is notorious for the debates it has fuelled about artistic freedom and censorship, charges of obscenity have tended to focus on more obviously disturbing works such as those of mutilated male genitalia. Indeed the Hayward will exhibit many of "the X port folio" sex photographs which prompted Senator Jesse Helm's wife to exclaim "Lord have mercy Jesse. I'm not believing this..." as well as a full-scale obscenity trial. The trial resulted in understandable paranoia in every American museum and funding body. Are we becoming similarly paranoid? Would the police have been invited to view this exhibition if it were being staged at a privately owned gallery like Saatchi's?
While there is undoubtedly a huge gulf between the language of art criticism and common-sense notions of decency, the current sensitivity about images of children produces the bizarre situation in which there is no such thing as an innocent image of a child, where a graphic portrayal of "fisting' is seen as less problematic.
We may be more aware of paedophilia than we were in 1976. But does that mean that none of us can see an image because a tiny minority may find it arousing? Such a fundamentalist argument would eventually eliminate the human body and its dangerous desires from art altogether, something which Mapplethorpe fought against all his life.
Is scouring images of three-year-olds for evidence of sexuality, theirs or ours, a good way to maintain public innocence? I doubt it somehow, but then Mapplethorpe's friends always did describe him as "a fallen angel".
"Mapplethorpe" is at the Hayward Gallery in London from 19 September until 17 November