How early escort-carrier conversion ideas began

How early were studies made for converting merchant ships into escort carriers?

The lineage begins in World War I with liner conversions such as Argus and continues through the interwar period before settling into the escort-carrier role.

The conversion lineage reaches back to Argus, built from a liner during World War I. Studies of liner conversions continued through the interwar years, while their intended role changed as carrier design and aircraft size developed. The Royal Navy's categories are described here as strike carriers, fleet carriers, and smaller cruiser carriers. Ark Royal illustrates the strike role, including attacks on targets in harbour, while the Illustrious class illustrates close work with the fleet. Unicorn, Argus, and Hermes appear among the models for the smaller category, whose duties included convoy escort and scouting. Those duties overlapped substantially with the later escort carrier's work. Pretoria Castle provides a further connection through its service as an armed merchant cruiser before conversion into an aircraft carrier.