And if nothing else, it's a really good exercise -- I now know things that I did not about what happened between LB and Dust! (Seriously. I knew nothing except "Time passed, Tirian did not regain his throne." And now I know more! Some of which foreshadows stuff in Dust!)

I don't know if Tirian is the worst king of Narnia; he may just be the unluckiest, since a lot of what happened is due to the choices his father made when he was king and the repercussions just happened to come after Erlian had died. On the other hand, losing one's country does not look particularly good on a resume. (And I think I like Jamie Bamber as Tirian more than I do my initial casting of Ewan McGregor.)