It’s come up a few times in my search list since episode 7 of The White Queen aired.
Did George, duke of Clarence, poison Isobel, duchess of Clarence?
George certainly thought someone poisoned her and reacted swiftly, to his ultimate detriment. He accused one of the duchess’s serving women, Ankarette Twynho, essentially abducted her and took her to Warwick, where she was tried and, not surprisingly, found guilty. She was immediately hanged. So far as I’m aware, the Queen, Elizabeth Wydeville, wasn’t implicated in this plot, nor did George hire a ‘sorcerer’ to determine the date of Edward IV’s death. George did a couple of other things that weren’t particularly helpful and was arrested and charged, initially, with bringing the law of England into disrepute. This was later changed to treason. In TWQ, the document that implicates him is a horoscope of Edward IV. Casting the king’s horoscope was certainly treason, as it ‘imagined the king’s death’. However, in reality, no such document was found. It’s likely that George kept a document left over from the Readeption which named him in the Lancastrian succession and this was deemed to be treason. (There’s more on their marriage, Isobel’s death and George’s subsequent behaviour here.)
So, in answer to the question “Did George Clarence poison Isobel Nevill?” I say very clearly and firmly: No.
Don’t forget to check out my reinterpretation of episode 7 here.