There’s a little-known side to the 19th-century American artist John Singer Sargent, and it is as far removed from the razzle-dazzle of his glittering career as a high-society portraitist as you can imagine. The artist who was famously described by Rodin as “the Van Dyck of our times” started his career emulating that great master of the seas, J M W Turner. He diligently honed his craft by painting dramatic seascapes, gentle coastlines and noble fishing folk. And if the 20-year-old Sargent couldn’t quite manage the roiling waves and lowering skies with quite the same level of brilliance as the English painter, he nonetheless possessed a quite remarkable artistic maturity. Turner, by contrast, couldn’t paint a convincing human figure for love nor money.