The evolutions of the concept of the DRA system, as implemented in Hong Kong, from the various hypothetical models promulgated in the UK and from the practical experience in the USA of Disputes Review Boards and Project Arbitration. Distillation of the role of the DRA from these sources, with particular reference to C Evans' 'independent intervenor', K Severn's Dispute Adviser, US Army Corps of Engineers Disputes Review Board, the research of the Center for Public Resources and the Foster- Conner Model.