‘I never travel without my diary. One should always have something sensational to read on a train.’ The Doctor gives River her diary in Let’s Kill Hitler… Find out more about Doctor Song!

To really highlight how vague and ambiguous even this information was, Steven Moffat himself retconned which Doctor took her ...

Or — could it be someone who zigged throughout the Doctor's life and took a lot of notes? Could this new boss be River Song? Admittedly, we've got little to go on when it comes to who Rogue is ...