Most of what I wrote is a combination of nuggets of knowledge I picked up from writing my undergraduate thesis on the topic of Alice Perrers and the instinctual knowledge that comes from loss, betrayal, friendship and love. The two primary sources I used were Thomas Walsingham's highly biased but usable source concerning the reigns of Edward III and his grandson Richard II, the Chronica maiora. Other information was taken from the very helpful and lively chronicles of Jean Froissart, who Queen Philippa patronized during her reign. They were fast friends, both being from the Vincennes region of Hainault, and he was seriously grieved to learn the death of his beloved patron. Other knowledge came from Barbara Tuchman's beautiful A Distant Mirror and numerous secondhand sources written primarily by Kay, Ormrod and Bothwell.
The details of Edward III's court are somewhat known, but what is less known is the details of the affair between Alice and her royal lover. It obviously happened. When it started is a mystery (I maintain by 1365 because her son, John of Surrey, was probably born 1365). Why is under the protection of unknowable human reasons, which I chose not to explore.
Until recently, it was believed Alys de Preston and Alice Perrers were the same people because of the simple similarities of their names. In the household accounts (the Close Patent Rolls) following Philippa's death in 1369, however, we can be sure they were different. My narrator was given the standard lady-in-waiting payment, while Alice Perrers was given nothing. Probably because Philippa felt she had already extracted enough from her household. There is evidence they were friends though. Alice Perrers was by most accounts clever and entertaining. They both shared a hatred of the Black Prince's wife, the Fair Joan of Kent, for example.
Alice Perrers became the king's mistress definitely by 1365. She saw England falter against the French host of the 1370s. She was one of the main players in the notable Good Parliament of 1376. She bore the King three royal bastards: John, Joan and Jane, none of whom had remarkable futures.
Her reign as such died when King Edward did. She was barred from the funeral of course. When Surrey Castle was demolished, however, historian Kay reports she was there to watch it. She had spent much time there with the King; she had had her first son there.
Other than the insults thrown against her, she was known as the Lady of the Sun, named at a great show of pageantry thrown by Edward III in 1374. Even the best historical records can't prove he loved her, or that she loved him. That's why we have historical fiction.
By all accounts, the events I mentioned concerning Queen Philippa's life are verified; she did famously plead for the life of the burgers of Calais, for instance. That is well documented. That she had a book of hours given to her with a kingfisher illustration in it is pure fiction. I thought a kingfisher was apt, though; medieval heraldry claimed they did in fact these birds calmed even the worst storms. Additionally, kingfishers are known to care immensely for their brood.