"I've always been a really big fan of Bruno, but when we worked together he was beyond. He can do anything, literally singing the best vocals you've ever heard live in your life while he is playing a drum or a bass or doing some mad percussion riff. I think he definitely will be the biggest, biggest, biggest artist in the world." British soul star Adele is full of admiration for Bruno Mars, who co-wrote All I Ask on her latest album, 25.