AN:
I got bored in class and wrote this, I don't know why but I think sometimes its good to write stuff like this to get a better idea of the characters.
Thin, wry and knowing. Often grim and painful, sad and regretful. Rare.
Arthur wasn't accustomed to many smiles from his father growing up. It was gift enough when Uther acknowledged him, let alone showed approval. Arthur knew that on some level his father loved him, but he knew better that Uther hated to show it.
His father seemed to think that any sign of love of affection, pride was a show of weakness to Camelot's enemies. Rather than what it what it actually would have been natural and necessary. But as they say hindsight is twenty-twenty and no-one's hindsight was clearer than Uther's.
Whenever Uther smiled at Arthur these days it was no less rare, but it was more knowing. As in, 'oh Arthur I know why you were looking at that young noblewoman' as if he had any idea of Arthur's taste in women.
It was nothing more than a belated attempt to show understanding, and one that Arthur thought often fell short. The only other kind of smile that Arthur got nowadays as crown prince, (apart from the endangered prideful smile that arose when Arthur managed to defeat an enemy), was Uther's sad smile.
The way that Uther's face contorted whenever he thought of his late wife, the wife he never spoke of but whose death caused Uther's vendetta against magic. This smile was sad and regretful, and very similar to Uther's smile when he thought of Arthur's lost childhood. If Arthur was braver he may have analysed the similarities but he realised that he preferred not to think about it.
If Arthur Pendragon was fond of introspection he may have hoped that his father's smiles were less rare, and less sad. But he couldn't escape the fact that he was just glad that Uther remembered he existed.
AN: Sorry I did not intend that to be so emo, I guess I always thought that Uther was a neglectful father. So caught up in his grief over Ygraine's death and his guilt and then his anger and rage over magic that he forgot he had a son. I don't know if anyone else thinks this, but I think that Arthur would be aware of this and feel somewhat sad.