I really want to give this story 5 stars, I know it is an important theme. But I think it is dragged out a little and could have been more concise. Where I have previously considered Peter Purves the best narrator of the range, I would retract that view for this one story because his rise-and-fall tones become part of every sentence, and just too predictable, although I prefer his disc overall.
The crucial story is very good. Neither narrator fully captivated me on this occasion forcing a relisten to most episodes. This is probably because the pace is just too slow as capable minds need more to keep them attentive. There are some nice scenes, and it is quite amusing at times. Purves does Hartnell beautifully so he should have done them on the second disc rather than have Maureen O'Brien impersonate a difficult-to-impersonate man.
Big Finish are certainly moving into more adult themes with series 4 and 5 of the Companion Chronicles. It does not bother me, but might affect some audiences.
A very good audio overall that perhaps should have been two long episodes, rather than 4 shorter ones. I don't like narrators needlessly padding my day out. When you listen to some other readings, the narrators are double speed at times trying to fit it in. The equivalent series five 4-episode story Peri and the Piscon Paradox (Doctor Who: The Companion Chronicles), also very adult at times, is an example of how a traditional four-parter is should be done, although I am would not want to encourage more than one a year.