When anyone can generate a convincing prototype, what makes a designer valuable? Your product owner walks into a meeting with a working prototype they built last night. How do you respond? Behind the screens lies an invisible game: the assumptions, incentives and pressures that shape what gets built, often before any work is shown. Drawing on banking examples and behavioural science, this talk explores how designers can question assumptions, make trade-offs visible and help teams act on evidence - including when it challenges their own ideas. You’ll leave with practical ways to make your thinking visible, bring clarity to difficult decisions and demonstrate the difference your design work makes for customers