Cullum's career really took off with the release of his album "Twentysomething" in 2003. Here, he reimagined traditionals and delivered original compositions that seamlessly blended pop, rock, and jazz. His distinctive voice, combined with his sophisticated playing style, has garnered critical acclaim and a dedicated fanbase. Cullum's ability to bend genres at will, as well as his songwriting contributions for other major artists, has solidified his reputation as one of the most versatile musicians of his generation.