With an estimated net worth of £1 billion, you would think Sir Paul McCartney might have acquired a taste for fancy food and attentive service. Sir Paul, 83, kept a low profile in sunglasses, a navy blue cap and a zip-up hoodie. The music icon, who led two legendary bands—the Beatles and Wings—makes a surprise cameo in the upcoming Spinal Tap sequel, Spinal Tap II: The End Continues, hitting theaters this September. 'I asked Paul McCartney about this. He concluded, '[Spinal Tap II] basically says: No matter how old you are, if you can still do it and still enjoy doing it, then do it.'