_The Evening Post_, 13 April 1925:
EXPRESS TRAIN SERVICE
SPEEDING UP IN SOUTH ISLAND
It is expected that an announcement will be made in about a fortnight’s time regarding the speeding up of the express train services on the South Island Main Trunk line. The running time of the through expresses from #Christchurch to #Invercargill, and vice versa, will be shortened by at least an hour, and the new schedules should be in operation by about the beginning of May.
https://paperspast.natlib.govt.nz/newspapers/EP19250413.2.115