Her. A banner was intended to indicate some distinctly valorous action of its user. The primary distinction between banners and standards and *pennons was that banners were square, having had the elongated fork-tail of the others cut off. Banners were meant to be of a size proportional to the owner's status, e.g. an emperor's was two or three times that of a *baron. A *badge would be shown on a banner for easy identification. The city of London's banner bore the image of St Paul in gold, with face, hands, feet in silver. It was borne out of St Paul's Cathedral's west door on occasions of battle, when Londoners were led by the lord of Baynard's Castle.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.