Now that the exhibition is installed, it is possible to get a sense of the full scope of its ambition before the crowds descend.   It’s on a grand scale, as Sidney Smirke’s galleries both allow and encourage, each space discreet, but flowing fluidly into the next.   The grandest of the galleries is devoted to an arrangement of metal bars in a wave, symbolising the lost lives of children in the 2008 earthquake in Sichuan owing to poor building construction.   96 tons:-