The mysterious hooded man who appears in the second half of this episode, and who revealed in 'Herne's Son' to be Robert of Huntingdon is not Jason Connery, but stuntman Graeme Crowther. This is not because Connery had not yet been cast, as the opening of Herne's Son: Part 1 (1986) was shot with this episode. It was a practical matter of scheduling, and the entirely physical and non-verbal nature of the role in The Greatest Enemy (1985).
This episode was originally meant to focus on the character of Nasir and his background as a professional assassin. However, as Michael Praed decided to leave the show for Broadway, the episode was substantially re-written at the very last minute. The earliest scenes in the episode, in which Nasir seems to leave the band, are from this abandoned script. The basic story of the original script was used as the B plot of the Third Season episode The Sheriff of Nottingham (1986).
The real reason for Robin of Loxley being killed off was that actor Michael Praed had received an offer he could not refuse from Broadway producers of the musical The Three Musketeers. The Broadway show, in which Praed played D'Artagnan, was not a great success. It closed after a week and only nine performances.