Check the odometer. The Proms deserve a jolly rev up when they start, and after 117 summer seasons, it was a fresh young pianist, Benjamin Grosvenor, who provided it. At nineteen, he came out in a casual shirt looking like a college freshman who might be spending his vacation as a pizza delivery boy or valet parking attendant. Those attendants are notorious for taking Porsches and Jags for a quick spin, returning them with hot wheels. Grosvenor had his chances with Liszt's Piano Concerto no. 2, but he returned it respectfully to its owner. He displayed glittering fingers and a beguiling soft touch at the beginning, but this work is faux art, setting a mood simply to tease the audience before the fireworks display.