A Protocol for the Investigation of Clinical Incidents (1999) was piloted on a Winnipeg high-risk neonatal service in 2001, and was subsequently adopted as the investigative tool of choice at the Winnipeg Regional Health Authority (WRHA). The paper describes the pilot and subsequent experience with the updated London Protocol (2004) in the WRHA Child Health Program. Themes include: tightly coupled systems; multiplicity of contributory factors; medication safety; predominance of "near misses"; authority gradient; professional accountability; partnerships; and implementation challenges. The London Protocol is an invaluable tool for review of critical occurrences and near misses. To maximize impact on patient safety, healthcare organizations must involve partners and develop expertise in human factors and change management.