The Southern Railway was formed in the railway grouping of 1923 and included the former London & South Western Railway. Its Cornwall network included the routes associated with Wadebridge and Padstow.
This was a different company from the Great Western Railway, which operated the main line through Cornwall and the Newquay branches. That distinction matters when comparing historical timetables or explaining how passengers moved between networks. The historical Southern Railway ended with nationalisation in 1948; its name should not be confused with present-day railway branding.
Sources
Source 1: https://kresenkernow.org/our-collections/collections-guides/transport/