Clara's prank gone wrong

It had been a joke. Ever since Clara had moved the vast library of Ashildr's past into their shared TARDIS, an impish part of her had entertained the idea of making Ashildr believe some rather outrageous things.

She hadn't taken it too seriously back then; it had been the early days. After that she'd started keeping her own diaries, at Ashildr's prompting, in an effort to deal with the memory loss that would no doubt plague her if she spent as much time as she planned taking the long route back to Gallifrey.

Which of course it had, meaning even she'd forgotten her little prank, her attempt at forging Ashildr's handwriting and adding to one of the journals. Some small quick thing to panic her, maybe catch a glimpse of something nice (ok, she could be a bit selfish), then explain and laugh over.

So when she heard a shouted 'oh no!' from the TARDIS library, she had no reason to not think it was genuine.

Ashildr spent most days going through her journals bit by bit; it had been a while since she'd started the cycle, and so in turn quite a while since she'd last read this journal, with Clara's doctored entry.