She figured largely in the movie "Braveheart". If there was an NPE in the British Royal line, it might have happened here, although no, I don't think it was William Wallace. My bet would be, oddly enough, Piers Gaveston, or one of her French attendants. I'm usually much against the romanticization of adultery, but in this case, more power to her.

Edward II

King Edward III

On the other hand, maybe he just looked like his mother.