It came sooner or later to distinguish the warship within the merchantman and, much more exclusively, the warship in commission from the warship laid up in harbour. The pennant is white inside the British Royal Navy, with a St. George’s Cross near the hoist, and denotes a warship in commission, https://donovanjwdnb.blogscribble.com/28177242/a-simple-key-for-medieval-banners-unveiled