1. Visor up: A number of accounts of the Battle of Towton, both contemporary and modern, remark on the fact that, although Edward of York was commanding the reserve force, he was constantly riding to the front lines to keep up his army's confidence, and that he was easily recognisable.
2. Judica me deus discerne meam de gente non sancta: A reference to this motto on a Lancastrian banner at Towton appears in a diplomatic letter to the Duke of Milan, dated 18 April 1461. The marguerites are the authors' invention, but they were the symbol of Queen Margaret, so we don't see any reason why not.
3. Tewkesbury: The Battle of Tewkesbury took place on 4 May 1471. Edward IV defeated the Lancastrian forces for the last time and all sources before 1500 record that Henry VI and Margaret's son was killed on the battlefield. Henry himself died in the Tower of London shortly afterward, probably on Edward's orders, thus wiping out the direct Lancastrian line.
4. The length was frankly terrifying: The Battle of Towton was the bloodiest battle ever fought on English soil. Contemporary accounts vary wildly, but the death toll is estimated to have been around 28,000, roughly 1% of the entire population of England at the time.
5. Quia ventum seminabunt et turbinem metent: Hosea 8:7, from the Latin Vulgate Bible.
6. Jack's height: Margaret of York's unusual height has been noted in a number of places, particularly in the context of her marriage to Charles of Burgundy, who was considerably shorter than her.
7. Gaveston: Referring to Piers Gaveston, favourite and probably lover of Edward II. He was executed by a rival faction, and Edward was ultimately deposed in favour of his son before dying mysteriously in prison.
8. Vae tibi terra cuius rex est puer: Ecclesiastes 10:16. Constantly invoked with reference to Henry VI, who became king when he was a baby. Edward V was a few months from his thirteenth birthday and had spent his childhood in Ludlow, raised by his maternal uncle, Anthony Woodville.
9. That woman: In May 1464, Edward married Elizabeth Woodville, daughter of a knight and the former Duchess of Bedford. The marriage, which introduced the Woodville faction to court, was partly responsible--along with Edward's alliance with Burgundy in 1468--for the estrangement between him and the Earl of Warwick that nearly cost Edward his throne.
10. Hunch: The legend of Richard III having a hunchback first appears in the Historia regum angliæ of John Rous, written after his death in 1485. None of the sources produced during Richard's lifetime, even those hostile to the king, give any indication of deformity.
11. Betrayed me: When Richard allied himself with Henry, Duke of Buckingham, and made his decision to take the throne, Hastings allied himself with Edward's Queen and her family. Richard discovered the plot and had Hastings executed with no warning on Tower Green on 13 June 1483.
12. Banished from his own kingdom: In 1470, the Earl of Warwick and Edward's brother George rebelled against him, and he was forced to flee to Burgundy. Six months later, he returned to England and defeated first Warwick and later Margaret of Anjou, thus cementing his claim to the throne. Richard of Gloucester, then eighteen years old, accompanied him.
13. Perkin Warbeck: In the late 1480s, a young man appeared in the court of Margaret of Burgundy, claiming to be Edward IV's missing younger son. He managed to garner quite a bit of political support in both Burgundy and Ireland, but was ultimately defeated on the field by King Henry VII and beheaded.