The ships commandant on a hospital ship was the Senior Medical Officer (Army Medical Corps) to whom the Company’s Captain and crew would defer.
Military hospital ships were protected by, and subject to, the Hague convention of 1907, which required that they be officially declared, certified and readily identifiable by a distinct livery. The ships were painted white with red crosses (sometimes illuminated) with a broad green band. They were well illuminated with a chain of green lights in addition to their deck and navigation lights.
Hospital ships flew the Red Cross flag and were identified by their own national flag. And under the rules of the convention, they were required to attend to casualties on both sides of the conflict.
108 merchant ships served as hospital ships during the war and over a quarter of these were requistioned from, and crewed by, P&O & BI.