Who is Enguerrand from A Distant Mirror: The Calamitous 14th Century and what is their importance?

Enguerrand VII is a high ranking official in the French court under the rule of King Jean. He is ransomed to the English for King Jean, during which time he meets and marries Isabella, the King of England's daughter. Enguerrand is married twice, fathers three daughters, and has one illegitimate son named Percy.