Just as the tapestry tells us nothing, so is the rest wishful thinking. The earliest evidence for someone who 'flew heraldic symbols or banners from horseback' is a seal of Raoul the Valiant (d.1152), count of Vermandois, where he is depicted carrying a lance with a chequered banner with three tails. His nephew, Waleran de Beaumont (d.1166), count of Meulan, had similar seals with chequers on his banner and later on his shield, saddle-cloth and surcoat. However, there is no evidence of chequers for any of their direct descendants. Waleran's mother, Isabel of Vermandois, by her second husband, had great-grandchildren who suddenly decided that they wanted to demonstrate their descent from Charlemagne through her and so adopted arms with chequers.
Since in general during the twelfth, thirteenth and fourteenth centuries knights helped themselves to coats of arms on their own authority, it is difficult to know when any such arms might have been 'granted by high authority'. I certainly can't imagine that the counts of Flanders and Hainault bothered with any higher authority for the arms that they bore from the last quarter of the twelfth century onwards.
John de Bado Aureo, writing his 'Tractatus de Armis' about 1395, says that 'whenever a man makes a petition for arms or some device, it is necessary to know about the man's habits, and thus can arms be suggested for him'. But note that he only says 'suggested', not 'granted'. And it was because coats of arms were starting to be used by unsuitable persons, that Henry V issued a writ in 1418 requiring everyone to show their right to bear arms (normally by long usage) 'those excepted who bore arms with us at the battle of Agincourt.' And of course the Tudor visitations were ordered because unsuitable people were still using coats of arms.
According to Rodney Dennys, 'Heraldry and the Heralds' p 46, the earliest existing English grant of arms is that by William Bruges, the first Garter King of Arms, to the Worshipful Company of Drapers of the City of London, on 10 March 1439.
Peter Howarth