The New Adventures of Robin Hood (1997) : 3x8

During an attack by Prince John's men on the village of Kingsgrove, Olwyn's acolyte Rowena accidentally sends Robin fifteen years back into the past, where he inadvertantly alters the course of history by rescuing a man who becomes a despotic king. Mortiana is working for him, and she has a magic duel with Rowena, from which Robin has to rescue Rowena before she is killed. The two of them have to work out how to undo Robin's act in the past.