How do you ensure requirements remain traceable on a long-running programme with multiple releases?

1. Maintain a single source of truth in a versioned tool rather than in circulated documents, so there is never ambiguity about which version is current.
2. Keep a traceability matrix linking business objective, requirement, epic, story, and test case, and update it as part of the definition of done rather than as a periodic catch-up exercise.
3. Use consistent unique identifiers across artifacts so a story in the delivery tool, a row in the requirements repository, and a test script all reference the same key.
4. Run traceability in both directions periodically: every objective should have stories delivering it, and every story should trace to an objective. Orphans in either direction are worth investigating — they usually indicate scope that crept in or value that was quietly dropped.
5. Keep a decision log alongside it, because on a multi-year programme the reason a requirement was changed is the first thing everyone forgets.