In 1787 critics of the Paris Salon were scandalised by a painting exhibited by Mme Vigée Le Brun. The subject was conventional enough: a self-portrait of the artist cradling her small daughter. The problem was that Vigée Le Brun was depicted smiling. You could even see her teeth. This was, as one critic put it, ‘an affectation which artists, connoisseurs and people of good taste are unanimous in condemning’.