Uther hates playing chess.
It's not that he hates the game, he just has terrible opponents. His son, Arthur, is a worthy match, but his prince duties are increasing lately and Uther is tired of Arthur's complaints that Uther 'only wins because he's the King'.
The problem is that it's true. No one wants to win against a King except another King. But how often does Uther get to challenge one except for endless bouts through letters?
Until -
Arthur: he's a terrible servant! He doesn't listen to me and treats me like a commoner!
Uther: *perking up* that servant?
Arthur: *realizing whom he's talking to* ... Yes, but- he's not that bad! An idiot, one who doesn't care about propriety but he's a good one. And it's sort of refreshing to not be-
Uther: You misunderstand. It's fine. Do you think he knows how to play chess?
Arthur: ... I don't know? I mean, he can read and write, which is surprising, and he speaks more languages than you'd expect, so maybe?
Uther: wonderful. I'd like to try it our
Arthur: *irritated* yes, Sire.
...
Uther: go on then. You do know how to play?
Merlin: *nervous* A little. My mother taught me
Uther: wonderful. And do not be afraid to put in a fight, I'm so bored of easy wins.
Merlin: am I not being executed if I win?
Uther: *shocked at Merlin's bluntness* excuse me?
Merlin: ... Am I being executed for asking?
Uther: ... I think this is gonna be fun. You take the white pieces.
Merlin: alright, Sire.
...
Uther: *shellshocked*
Merlin: may I leave, Sire?
Uther: how on earth did you-
Merlin: I was allowed to win, right?
Uther: of course. But how-
Merlin: it's in the strategy. You like to sacrifice your pawns to make space for your knights and bishops. And you barely move your Queen.
Uther: I'm protecting the King! The most important piece on the field!!!
Merlin: A good King wouldn't sacrifice his people for no reason. There is no shame in trying to save them all.
Uther: that's what Arthur would do and how he would keep losing. You didn't do that at all! You basically sacrificed every single piece on the field in a suicide mission!
Merlin: *blinking dumbly* I'm protecting my King. The most important piece on the field.