Royal Standards of England

The royal standards of England were narrow, tapering swallow-tailed heraldic flags, of considerable length, used mainly for mustering troops in battle, in pageants and at funerals, by the monarchs of England. In high favour during the Tudor period, the Royal English Standard was a flag that was of a separate design and purpose to the Royal Banner. It featured St George's Cross at its head, followed by a number of heraldic devices, a supporter, badges or crests, with a motto—but it did not bear a coat of arms. The Royal Standard changed its composition frequently from reign to reign, but retained the motto Dieu et mon droit, meaning God and my right; which was divided into two bands: Dieu et mon and Droyt.

There were three main types of heraldic flag.

Inspire us with the spleen of fiery dragons..... Shakespeare. Richard III. act v, sc.3.

The medieval standard was usually about eight feet long, but Tudor heralds determined different lengths, according to the rank of the nobility. "The Great Standard to be sette before the Kinges pavilion or tent – not to be borne in battle" – was 33-foot long. A duke's standard was 21-foot in length, and that of the humble knight, 12-foot long. These standards, or personal flags, were displayed by armigerous commanders in battle, but mustering and rallying functions were performed by livery flags; notably the standard which bore the liveries and badges familiar to the retainers and soldiers, of which their uniforms were composed. The St. George in the hoist of each standard was the communal symbol of national identity. This badge or banner of England, at the head of the standard, was the indication that the men assembled beneath it were first, Englishmen, and secondly, the followers of the man whose arms were continued on the standard.

...
Wikipedia