Now that was a good thing to remember next time Merlin made a pest out of himself...

Arthur had given up on keeping his mouth shut, but he still - methodically - bit down on his lip every time anything loud wanted to escape. He had a single-minded focus going on right now. A bit like battle.

Except a great deal more pleasant.

He was quickly losing track of his mind entirely as his hand began to move, sliding up and down.