Who is Tasha Lem?

Besides being the Mother Superious of the Papal Mainframe, she’s probably River Song isn’t she? There are too many similarities for it not to be (a very forward psychopath in a relationship with the Doctor), and it makes sense for her to be in the Eleventh Doctor’s last episode somewhere, so it’s probably River, QED.

Only then we have to ask where the Tasha Lem incarnation fits in to River or the Doctor’s timeline.

Where might Tasha Lem fit into River’s timeline?

We might not find out onscreen, though we don’t know what happened to River between regenerating in Sixties New York and being Mels alongside her parents in Leadworth, so it probably happened there. However, this allows for the possiblity of Tasha regenerating, and she was meant to have died. If she is River, then she could occur after Silence in the Library/The Forests of the Dead. Churches do go in for resurrection, although not usually by extracting assassins from one of their breakaway sects from a computer in the future.

Steven Moffat has said that River won’t be involved from now on except for story reasons, if someone comes up with something where her presence fits. However, Moffat lies. Obviously he does. Not only has he said so, but Doctor Who isn’t even real. We’ve checked and everything.