Confusingly, this 4th episode has the on-screen episode title graphic stating "2. The Queen of Spain's Beard", obviously as it was originally intended as episode 2. Officially, the reason for the swapping the original broadcast order of episode 2 & 4 was that "The Queen of Spain's Beard" was not ready. It's more likely however, that they were actually swapped as a simple artistic choice as episode 4 makes a stronger second episode for a brand new series. Some series 1 compilations return these 2 episodes to their originally intended position in the run, not the original broadcast order.
The trivia item below may give away important plot points.
Edmund's arranged marriage to Princess Leia of Hungary is a reference to the arranged marriage of England's King Richard II to Princess Isabella of France when she was just six years old. It being a strictly political move, the marriage was of course non-sexual, and there was an option for her to dissolve the marriage when she turned 12. This became irrelevant when she was widowed at age 10.