And then Arthur's knee was between his legs, edging them apart and whatever other weak noises of surprise, or objection or outrage, Merlin was about to make were swallowed by Arthur's rumbling groan as he shifted their hips together—immediately grinding down on Merlin's leg. Merlin closed his eyes, then, screwed them shut and tried to breathe and work out what was happening before it could keep on happening. But the next moment Arthur had worked his arms above his head, pinning them down, the next he was rutting up against him and the next his breath was coming in hot puffs on Merlin's cheek and he could feel Arthur so clearly, even through that fabric, heavy and strained and moving against his thigh.
I lied...This is the hottest one I've ever read. I'm pretty sure I've never been this breathless. Holy jesus fuck.