'Until the last dog is hung' originates with Henry VII. At the conclusion of the War of the Roses, Henry VII pitted a pack of dogs against a lion to demonstrate what would happen to traitors in his kingdom. The lion lost--which is not what Henry expected. To make his muddled point clear, Henry had every dog hung--and made his nobles watch till the last of them was dispatched. The story is related in The Autobiography of Henry VIII by Margaret George.