Hmm, I prefer Channing to the Master. I find Channing's flat and emotionless delivery more eerily 'fake' and disturbing than the Master, who is a bit of a pantomime villain.

Robert Holmes did tend to write Jo as a silly girl rather than the competent secret agent seen in some other scripts e.g. The Curse of Peladon, The Sea Devils, Frontier in Space (the latter where the Master fails to hypnotise her).