So he kisses back at length, and then slowly moves his way down Lanselos' body. It's not as if he hadn't imagined this, back in the day--had fantasies about what he'd do if he weren't the king, if he dared to try and join them. He can imagine it now.
In a way, it's terribly important that he do it like this. He doesn't want to touch Lanse just with his hands. It's better to use his mouth anyway, he has a better handle on the nuances of pressure that way; but it's not just that. The last and only time he was at Lanselos' feet, it was with Gwenore's bullet in his arm, on the firing range. Somehow this feels like the only way to make any kind of reparation.