A Regulatory Perspective (2025–2026). UK Financial Services regulation in 2025–2026 increasingly requires firms to demonstrate not just what is true today, but what was known at the time decisions were made. Across Consumer Duty, s166 reviews, AML/KYC, model risk, and operational resilience, regulators expect deterministic reconstruction of historical belief, supported by traceable evidence. This article explains where that requirement comes from, why traditional current-state platforms fail under scrutiny, and why preserving temporal truth inevitably drives architectures that capture change over time as a foundational control, not a technical preference.