Dusk was settling over the desert and a vast car park behind Caesars Palace in Las Vegas, where a stadium had been built to house the world-title fight between Muhammad Ali and Larry Holmes, exactly 40 years ago next month, when veteran ring announcer Chuck Hull called for quiet before the bout began. "Pray silence" he requested, "while Gladys Knight, of Gladys Knight and the Pips, sings our glorious national anthem."