The Rembrandt and Turner exhibitions, one at London's National Gallery, the other at Tate Britain, are populist homages to two of the undoubted giants of the European cultural tradition. They do not attempt complete surveys. Instead they seek to found themselves on a now well-established but in fact comparatively recent myth: that of a 'late style', wherein a great artist, nearing the end of his life, somehow transcends all the works he has made previously. Titian and Michelangelo have also been the subjects of the same kind of mythologisation. The facts are, of course, that neither Rembrandt nor Turner attained a very great age by 21st century standards. The Rembrandt show covers the artist's last decade-and-half, roughly speaking from the time when he went bankrupt in 1656 to his death in October 1669, aged 63. Turner had a longer life, but the show at Tate Britain covers about the same amount of ground - from 1835, when the artist was sixty, until his death in 1851, aged 76. The idea of the 'late style', as a very special, magical phase in the evolution of the work of a great artist, is, as I have just said, a comparatively modern invention.