During production of this story, new producer John Wiles began taking over production duties. William Hartnell, displeased at the number of changes undergoing the production, play-acted throwing a temper tantrum during the rehearsal of this story.
The Monk was the first Time Lord other than the Doctor and Susan to appear in the series, although the term Time Lord would not be invented for another four years. The Monk also became the series' first recurring individual villain.
It is evident that this story was produced in the 1960s: all the Monk's possessions are contemporary with that era, and he refers to the TARDIS as a "modern" police box. Only his gramophone is old-fashioned, and it was intended to be a tape recorder in the script.
The story's historical setting had a particular relevance in 1965 as the 900th anniversary of the Battle of Hastings was only a year away. Production constraints meant that the series could not satisfactorily feature the battle, but nor could it be fully ignored, hence the period was taken for the setting.
When the Doctor and Stephen are looking at the Viking helmet, the Doctor uses it as evidence that they have travelled in time. Stephen replies that it could be from a costume. Given the helmet had horns, it was not true to the historical helmets worn by Vikings (which did not have horns). The addition of horns to a Viking helmet is a product of theatre and opera productions, and, therefore, Stephen's guess was closer to the truth.