Ooh, this is gorgeous! Funny and sexy, with such strong overtones of the Doctor's sense of humour. He's not really punishing Jack - he'd do something far worse than that if he really intended to punish him. And I bet he's grinning inside at this:

"I do my best work on my knees, Doctor." Full of faux innocence. And promise.

Any chance of the sequel in which Jack proves he's as good as his word? I'm sure Rose would love to be a witness! *g*