He was not the product of an ‘affair’. His date of birth is all wrong for that.
He was in fact a great favorite of the Queen and the UK generally - probably spoiled rotten - until he showed himself to be a complete louse.
What she and the rest of the family and courtiers did do, was HIDE his stupidity, dreadful behavior ( as much as they could ), and gross acts, some of which he spilled and/or exaggerated in "THE SPARE".
Lady C. is going to have a high old time, on Saturday and River might put something out today! :-)