I'll start out with Martin and historiography of late medieval knighthood and chivalric culture (this is, in part, to dispel some of the commonly held beliefs about knighthood like the, now deleted, response I saw here earlier).

Firstly, Martin is not, and his books are not, historical sources. They scrape historical phenomena and splashes them into his cooking pot to create a distinct world. This creates a mess for claims of historical accuracy, as phenomena particular to the ninth- or twelfth-centuries are currently occurring in a context more particular to the fifteenth-century. This essentially means that all of these events play out anachronistically and some are theoretically impossible.

Martin's knighthood, or his concept of knighthood, is, I assume, mostly informed by the c.1890-pre-1984 historiography and popular conception of knighthood. In the 1700s and 1800s public and historical reception of chivalry oscillated between lauding and trivialising the subject. It was either Sir Walter Scott's Ivanhoe or an elaborate ruse. In the late nineteenth- and early twentieth-century this cynical attitude towards knighthood and chivalric culture hardened, especially due to the influence of two key texts (Johan Huizinga's The Waning [or Autumn] of the Middle Ages and R.L. Kilgour's The Decline of Chivalry, both published in the inter-war period). I have discussed Martin's treatment of knighthood and chivalry in some more detail, here.

For historians, the legacy of the early twentieth-century resulted in two narratives emerging: the first was that Christianity and courtesy ‘tamed’ the violent warrior impulses of the martial class. The second was that chivalry entered a decline in the fourteenth- and fifteenth-centuries, as evidenced in the contemporary literature. The first narrative was deconstructed by Maurice Keen and Jean Flori in the 1980s who demonstrated the secular origins of chivalry – emerging in the twelfth-century. While David Crouch has argued that chivalry was the conscious form of the unconscious code known as the ‘noble habitus’. The ‘decline’ narrative was also addressed by Keen but is still popular among military historians – Lawrence Marvin in his military account of the Albigensian Crusade refers to knighthood and chivalric values once, in his introduction, and discards the entire ethos as unimportant due to the nature of the war (sieges and raids). Recently Kaeuper and Craig Taylor have demonstrated that the literary basis for this narrative is flawed. It does not account for the fact that knights and writers had always complained about declining standards and looking back to either the Romans or mythologised figures such as King Arthur for a ‘golden age’ of chivalry.

Onto the matter at hand, dubbing and the receipt of knighthood. Knighthood in England, if this is truly set during the Wars of the Roses, carries a greater bureaucratic weight than it did martial. From the mid thirteenth-century onwards there had been a real decline in the numbers of dubbed knights due to a combination of increasing costs and bureaucratic (at a local level, but on the crowns behalf, such as sheriff or bailiff) duties associated with the taking of the title of knight. Many people simply didn't want to become a dubbed knight or take on the bureaucratic duties of a knight. This led to the contraction of a dubbed knightly class and the beginning of a trend towards exclusivity: dubbed knighthood became the preserve of the rich, powerful, and politically inclined.

The point of the above is to provide context to what being a knight meant. It was not just about being a warrior and thus your capacity for being a warrior capable of holding their own against all others was not the chief and determinant factor for receiving knighthood.

A common occasion for dubbing, from the thirteenth-century onwards, was on the eve of battle (or storming a fortress). Here is the (possibly fictional) speech of King James of Portugal addressed to the sixty Portuguese and English squires on the eve of the Battle of Aljubarotta (1385):

this order of chivalry is so high and so noble, that he who is a knight should have no dealing with anything that is so low, with vile things or with cowardice, but he should be as hardy and as proud as a lion in pursuit of his prey. And therefore it is my wish that this day you shall show such prowess as it befits you to show: that is why I have set you in the van of the battle. There so do that you may win honour; otherwise your spurs are not well set upon you.

Ouevres de Froissart, ed. K. de Kettenhove, xi, 166. Translated in Maurice Keen, Chivalry, London, 1984.

These squires were knighted before the battle and were expected to live up to the values of chivalry. Knighthood was an inducement to courageous and bold action. The more common romantic images of the receipt of knighthood for deeds of arms and prowess are found more commonly in romance. This is perhaps unsurprising when, it has been argued, these texts were likely written for aristocratic and noble youths and possibly tailored for such an audience.

The events Martin describes are not impossible. I cannot think off the top of my head a precedent, other than literary ones. I think it is unfair to compare a knight's duties to a modern sportsman, and would point out that the chief attribute of a knight is his hardiness, his stamina, and his endurance.

One need not be the best knight in the world to be a knight, nor an adult. Henry VI, son of Henry V, was knighted at the tender age of five years old - in part because his duties, the duties of the monarch rather than the toddler, required him to be dubbed.

Bibliography

Crouch, D., The Birth of Nobility: Social Change in England and France, 900-1300, Harlow, 2005.

Huizinga, J., The Waning of the Middle Ages, modern trans., Chicago, 1996.

Kaeuper, R., Chivalry and Violence, Oxford, 1999. | Holy Warriors: The Religious Ideology of Chivalry, Philadelphia, 2009.

Keen, M., Chivalry, London, 1984.

Kilgour, R.L., The Decline of Chivalry as shown in the French literature of the late Middle Ages, Cambridge, Mass., 1937.

Flori, J., L’Idéologie de glaive, Genève, 1983. | L’Essor de la chevalerie, Genève, 1986.

Marvin, L.W., The Occitan War: A military and political history of the Albigensian Crusade, 1209-1218, Cambridge, 2008.

Taylor, C.D. , Chivalry and the Ideals of Knighthood in France During the Hundred Years War, Cambridge, 2013. Preface available here and introduction available here.