This case, a follow-up to “Design Thinking in Action (A): South Western Railway” (UVA-S-0377), finds South Western Railway (SWR) and its design-consultancy partner, DK&A, beginning work on a project to improve passenger experience. The team followed a classic design thinking methodology, the Double Diamond, focused on four steps—discover, define, develop, and deliver—and created an ambitious three-month schedule to meet a tight delivery deadline. The case describes in detail how team members gathered data from a variety of passenger categories, created persona types and journey maps, and identified new ideas to help SWR accomplish its goals. It concludes with questions about how these ideas should be tested. What design should experiments take? What outcomes were most important to measure and learn from?