There’s something almost secretive about the entrance to the Royal Academy’s Spain and the Hispanic World: Treasures from the Hispanic Society Museum & Library. Two unprepossessing portals either side of an oddly blank dark space have just a hint of vacuum pressure behind them. Once through, it takes a moment for the eyes to acclimatise to the gloom: the spaces that were filled with light and garish colour for the Summer Show are now in near blackout, with the skylights covered over and the walls painted an unpromising shade of greyish blue. And then, with the clunk of the closing door behind you, you realise that you are surrounded by treasure.