[spoilers] Jo/Miranda Raison

[Adam Carter]

I thought Jo had one of the best arcs of the entire show. I'd even go as far as to say that she was possibly the most well-developed officer.

Jo started off a naive and wide-eyed young recruit, but eventually molded into a hardened, seasoned officer. I wouldn't be surprised to find out that her dramatic hair change from Series 4 to Series 6 was an intentional reflection of this.