In the beginning, chaos prevailed… Everything changed when WSP’s UK Systems Engineering & Integration team codified the systems integration (SI) processes and techniques we were applying in major railway programs. Each new megaproject could then benefit from WSP’s proven SI approach that provided an enlightened perspective and a clear path to deliver targeted client outcomes. Today, SI:D3 reflects years of learning by doing. A brief tour through history offers insight into why SI:D3 is a timely approach for current complex programs.