Not all work was postponed by the war. A campaign to extend the line from Culverden to Waiau was successful and construction continued through the war, with the line opened to Waiau on 15 December 1919. This boosted the hopes of those seeking an inland route, and more work was undertaken, with 3 km of formation built for a line from Waiau to Kaikōura, but ultimately nothing came of this proposal and the terminus remained in Waiau. The 1920s saw little progress made on the Main North Line as various interest groups, governments, and expert reports contested to achieve their respective desired outcomes. At this stage, both the Leader Valley and Tophouse routes were still possibilities, but it was around this time that proposals of a route out of Parnassus in a more easterly direction than the Leader Valley began to be formulated. This became the present-day route.