Talk about a promise you've broken.

It was an extravagant room, the room he gave her on the TARDIS. Her own room, the first of the sort that she had ever owned if you didn’t include the shuttle she had commandeered. And she liked it. Oh, she loved it. It was far better than the cramped quarters she had glimpsed on Messaline and far better than anyone else’s bedroom that she had ever seen (all of two, accidentally while cutting through houses to escape a trio of angry mobsters on Stars’ End).

But this room? It was luxurious, decadent even. Not quite as fascinating as his bedroom, but completely made up for by the fact that it was hers. Hers, he said, to do with as she liked. To entertain her own visitors in, to relax, to practice the lessons he taught her within. It hadn’t cost much, this room with the luscious scarlet carpet (the colour of Gallifreyan blood she had noted with a sardonic laugh) and the king-sized bed just as perfect for fucking as his was. It hadn’t cost much at all.

( It had only cost a promise and not even a promise made to any particular individual. )