I clocked that she was the fugitive very quickly - Lee was just way too suspicious to be the actual target - and that she was a rogue Time Lord using a Chameleon Arch as soon as Gat said Lee was her 'faithful companion.' But I had absolutely no clue about the real twist until Thirteen hit the TARDIS with that shovel. Amazing!

Much like that outfit, which debuted extremely high up in my 'favourite things the Doctor has ever worn' list.