Speaking to BANG Showbiz, Matt said:
“I think River’s too independent to ever be a full-time companion, I think that’s what makes River great as a character. The companions and The Doctor are doing their thing then whoosh in comes the hair!
“It just messes the Doctor up and makes him go, ‘Oh Christ, River’s here,’ and it frightens him. And weirdly he’s going, ‘Why the hell am I attracted to her? What’s that?’ That’s the woman who makes him go whoa.”
Matt added: “She’s back for episode eight and she definitely appears in nine and thirteen and she’ll be back again. River’s not going anywhere.”