For those whining about it should be a UK act, all the big UK acts will be performing at the opening and closing ceremonies, no foreigners allowed as it will showcase British talent (including Adele). I don't consider this festival to be the Olympics "headliner", there are a ton of musical events on before, during and after the Olympics here in the UK this summer. I like Rihanna personally but her lazy-ass live performances are not fit to headline anything. We see Gaga and Beyonce doing vocal warmup exercises before they go onstage, we see Rihanna pissing about with her friends. That says it all for me. She is a good recording artist but a poor live one, and that is why her tours are not mega-popular, unfortunately, as she only needs some lessons in vocal technique so she can perform onstage like she does in the studio.