This document discusses challenges with effectively leveraging lessons learned from past projects. It notes that while trillions are spent annually on projects globally, lessons learned systems often do not work well to avoid repeating mistakes. The document analyzes lessons learned data from over 50 organizations and 1,000 projects, finding issues like a lack of context, root cause analysis, and measurable actions. It argues for a more data-centric approach to link lessons to risks and enable different perspectives to utilize the information. The document provides an example of how Crossrail leveraged experience across similar projects.