On a windswept hilltop just off the A637, midway between Wakefield and Barnsley, stands a shiny sculpture that seems utterly at odds with the rugged scenery which surrounds it. Robert Indiana’s Love (1966) is an icon of 60s and 70s Americana, as redolent of that hedonistic era as Robert Crumb’s Keep on Truckin’ (1968). It is the centrepiece of a bold new show at Yorkshire Sculpture Park, which sheds fresh light on this enigmatic artist, whose most famous image has overshadowed his more intense and thoughtful work.