User blog comment:Morganaforever/Morgana's torturer in 5x08/@comment-5204542-20121118150837/@comment-5674726-20121118160114

But the would-be ally could still miscalculate and believe that they would gain favour with Arthur if they told him that they gave him two Morgana-free years.

If Arthur does learn of her imprisonment and torture, his reaction could impact his view of Morgana. He's asked her what happened to her and this is a piece to the puzzle.