This essay examines how literature and popular music documented and shaped Britain's transformation from military empire to cultural soft power in the post-World War II era. Through analysis of three pivotal cultural moments—Sam Selvon's The Lonely Londoners (1956), the Beatles' Revolver (1966) and Sgt. Pepper's Lonely Hearts Club Band (1967), and Zadie Smith's White Teeth (2000)—the study traces Britain's evolution from imperial certainty through post-colonial anxiety to multicultural complexity. Selvon's novel exposes the gap between Britain's self-image as a tolerant Commonwealth and the lived reality of Caribbean immigrants facing what Moses calls "the old English diplomacy" of polite exclusion. The Beatles' revolutionary albums capture a nation learning to project global influence through cultural innovation rather than military force, transforming imperial imagery into psychedelic spectacle. Smith's millennial novel presents the multicultural Britain that emerged from these transformations while diagnosing tensions that would culminate in Brexit. Together, these works reveal how artistic production actively participated in constructing new narratives of British identity, using linguistic innovation and formal experimentation to challenge imperial hierarchies. The analysis demonstrates that Britain's transformation remains unfinished, with imperial structures persisting beneath multicultural celebrations, revealing fundamental contradictions about belonging, identity, and national mythology that continue to shape contemporary Britain.