River Song is something of an enigma to me. On the one hand, I think she’s fabulous, engaging and one the most inspired characters in the series. On the other hand, I think the series does not take allow her to live up to her full potential. I’m tremendously glad that the character came on the scene while Davies was still running the show; had Moffat been in charge by then, I have a sneaking suspicion that Alex Kingston may very well have been passed over for someone looking at bit more like Amy and Clara. And I don’t know about you, but the idea of ANYONE else in the role of River simply does not compute. Kingston positively OWNS that role. Even in episodes where the character is forced to act very much like a Mary Sue, Kingston manages to stay authentic to the underlying identity and enjoy every minute of it.
I would love to see Kingston return to the series to interact with Capaldi; were she to do so, I predict fireworks of the best kind.