I read that book in my ‘teens. John of Gaunt is one of the key figures of the period, a classic strongman.
Regarding the article, piffle. The connection between the Mountbatten-Windsors and the House of York is completely irrelevant. Parliament made William of Orange king, and Parliament made George of Hanover king.
“Katherine Swynford” by Alison Weir is a more scholarly treatise on the same subject, also worth the read IMHO. (My interest stems in part from my relationship to the deRoet family and part from my love of the study of history...that and $2.00 will get me a cuppa tea anywhere)
Still, the issue of their legitimacy was a touchy subject for the Tudors. Henry VII put to death Edward Plantagenet, the Earl of Warwick, extinguishing the male Plantagenet line. Henry VIII executed Margaret Pole, Countess of Salisbury, another Plantagenet.
It is an interesting fact however, that could lead to plenty of speculation as to who the cuckold was back in the chain of descent.
(Note sacks of payola!)