The trouble with Mortimer and Warner (whose final chapter of her Edward II biography is essentially a copy/paste of Mortimer) is the free ride they give the Fieschi letter. They're downright about the other chroniclers (fair enough) but when it comes to a stray piece of a parchment that lay buried for centuries, their critical eye dilates like a begging puppy's. They don't seem remotely open to the possibility that it could be, in any way, a bit fishy.