A/N: This was written before The Poisoned Chalice, so the fact that it rather echoes the dialogue from the end is just a coincidence.
Disclaimer: Merlin isn't mine. I wish he was...
Arthur has his suspicions. Sometimes he wonders if Merlin thinks he's blind (though he has been helping that idea along a little). Merlin does things there's no way he should be able to do. Strange things happen when he's around. Of course Arthur is suspicious.
He knows he should really tell his father, but he also knows Uther trusts him enough to have Merlin executed, just because he's suspicious, and... what if he's wrong?
Besides, even if he's right, he can't lose Merlin. Because... well, then he'd have to find another servant.
That's the only reason he doesn't tell his father.
Really.
Well?