Duke of Roxburghe

John Ker, 3rd Duke of Roxburghe, was a Scottish nobleman, a keen bibliophile and collector whose wealth gave him every opportunity to indulge his passion. After he died his great library was dispersed. It was the prospect of this sale which so excited the cupidity of Mr Norrell that he readily consented to the departure of his pupil, Jonathan Strange, for the wars, so that the latter might not bid against him for any of the treasures he confidently (and rightly) supposed the collection might contain[28].

For further information on His Grace, consult the article in wikipedia.