Before revision: Before World War II ships were collected into divisions derived from the Royal Navy's "division" of the line of battle in which one squadron usually remained under the direct command of the Admiral of the Fleet, one squadron was commanded by a Vice Admiral, and one by a Rear Admiral, each of the three squadrons flying different coloured flags , hence the terms flagship and flag officer.
After revision: Before World War II ships were collected into divisions derived from the Royal Navy's "division" of the line of battle in which one squadron usually remained under the direct command of the Admiral of the Fleet, one squadron was commanded by a Vice Admiral, and one by a Rear Admiral, each flying a different command flag , hence the terms flagship and flag officer.