He missed that grin, he realised, unbuttoning his shirt-cuffs with two nimble flicks of his fingers and then moving to the row of buttons down his front. He hadn't seen it much on this face - he hadn't exactly given the Doctor much cause to smile, on the Valiant - but when he had, it was the kind of grin that one couldn't help but return.
So he grinned back, a grin that was a little rough around the edges, a tiny bit crazed, a tad uncertain, but a grin nonetheless. He took his shirt off and flung it towards a nearby chair - no need to fold it; this was his room and he had another twenty hanging ready in the wardrobe - then turned back to the Doctor with a rather Masterly glint in his eye.
"On your back, Doctor. Let me finish what I started."