Laughing and dropping clothing, Watson twisted away, more out of some feeling that he couldn't let Holmes get away with that than with any real desire to leave Holmes's arms. Entirely abandoning his burden of clothing, he reached to give Holmes a swat on his bottom, his expression as stern as he could manage. Pulling himself close, he gave Holmes's arse a squeeze and kissed him.

"If I don't get to keep my dignity," he said, still with an eyebrow raised in an attempt at severity, "then neither do you."

After another, gentler swat he pulled away and bent to pick up the scattered clothing he had dropped.