ishipjawnlock
Of course, the spell would not be broken by our kiss. But certainly, Lady Vivian bursting through the tent's entrance would. "Arthur?" - speaking of the devil - "I come here to.. Only to find you bedding another girl?!"
Arthur's warm, wet tongue teased at the parting of my lips, but I could not bring myself to get lost in our kiss while we were being watched. "Your servant, seriously?!" She shouted, and shook her head once I looked at her with the most embarrassed face I could manage.
"H-He kissed me."
OR
Arthur gets enchanted by a love spell. Merlin accidently lifts it.