The story begins in 1400, the year after the deposition of Richard II of England by Henry of Bolingbrooke, thereafter Henry IV. Lord Gilbert Reginald Falworth is attainted for being King Richard's councilor, who strongly advised him to resist his cousin Henry's movement to seize the throne, and for protecting The Earl of Alban, a fictional conspirator against the succeeding King Henry. Falworth is blinded in a trial by combat with William Bushy Brookhurst, later created Earl of Alban, whom young Myles, son of Lord Falworth, remembers brutally killing Sir John Dale in the hall of Falworth castle where he lived with his parents.
Lord Falworth, his wife, Myles, and Diccon Bowman go into hiding in Crosbey-Dale (pronounced, kris' b�-d�l) on the estates of the Priory of St. Mary, under the protection of the elderly Prior Edward. Most of the action of the novel is in Derbyshire, England; the ruins of a Mackworth Castle actually exist on the west side of Derby. Diccon Bowman undertakes the physical training of young Myles, and Prior Edward performs the academic training. Lady Falworth teaches him the French language. Myles is a champion wrestler, defeating a man a head taller than he. Later in the novel the reader learns that Myles as a child took a dangerous ride on a country windmill.
In 1408 when Myles is 16 years old he is taken to Devlen castle, the seat of the Earl of Mackworth, kinsman to Lord Falworth. There he is enrolled as a squire by Sir James Lee, an old friend of his father's and Diccon Bowman. Sir James advises Myles to be discreet about matters concerning his family since his father had been attainted as a traitor to the king.
Another squire, Francis Gascoyne, became Myles's good friend, who defended him in his struggle against the head-squires (the bachelors) led by Walter Blunt. There had been a pecking order established by which the bachelors forced the younger squires to serve them. Myles, Francis, and eighteen other lads formed what they called the "Twenty Knights of the Rose" as a fellowship to promote justice among the squires and end the hierarchy established by the bachelors. The "Knights of the Rose" met in a hideout discovered by Myles and Francis at the top of the oldest part of the castle, known as the "Brutus Tower," which they called their Eyry (hawk's nest). After two fights with Walter Blunt, Myles and his "knights" win a skirmish with the bachelors in which Blunt is gravely wounded by Myles for the second time. The bachelor's routine is ended. Walter Blunt is made a gentleman-in-waiting by the Earl Mackworth, and he is no longer mentioned in the novel.
When retrieving a ball he had used in play with his friends, Myles makes his way over a wall into the "privy garden" used by the Countess Mackworth and her household, and meets Anne, the earl's daughter and Alice, the earl's niece. Anne is a few years older than Myles, but Alice is just his age so he begins to consider her his lady fair and a possible wife. Seven times he climbs over the wall to meet with the girls to tell them about his exploits. The last time Earl Mackworth himself sees him trespassing and puts a stop to it. The reader is told later that Myles's father had his mother write Mackworth to advise him to do this. Myles escapes being severely punished for his actions as two other young men had been for venturing into this forbidden area.
Unknown to Myles, his father and Earl Mackworth, who also was an enemy to the Earl of Alban, plan to have Myles knighted by the king as a Knight of the Bath to make him eligible to champion and exonerate his father on the field of battle in trial by combat. This is done during a royal visit to Devlen castle in 1411 in order to have Myles oppose the French jousting champion of the Compte de Vermoise, Sieur de la Montaigne. Sir Myles succeeds in unhorsing this knight fairly in a joust. Sir Myles with his chosen squire and friend Francis Gascoyne accompany the Earl Mackworth's brother Lord George Beaumont into France for military maneuvers in the French Dauphin's service. After six months he is recalled to London by Earl Mackworth to oppose the Earl of Alban. To further facilitate this Sir Myles is transferred from Mackworth's household to that of Henry, Prince of Wales.
Myles's parents are brought to London to join their son before the king as their grievances are presented to him. Myles throws down his gauntlet before the Earl of Alban, initiating trial by combat. The ailing King Henry suspends these proceedings until the "High Court of Chivalry" can render a decision about the legality of the matter. After two months they find that Sir Myles Falworth may justly fight Alban. The battle is set for September 3, 1412. Sir Myles shows himself a more chivalrous knight than Earl Alban had been by giving his opponent quarter three times. This almost costs him his life, but in the end Sir Myles prevails in conquering his enemy. The king refuses to restore all the estates of Lord Falworth, but with the accession of his son, King Henry V of England, the following January the fortunes of Falworth and Mackworth are secured. Sir Myles marries the Lady Alice and lives in Falworth castle as his home with Sir Francis Gascoyne and Sir James Lee.

Question: How old was Myles when he was enrolled as a squire?
Answer: 16
Alternative answer: Sixteen years old.