User blog comment:LokiIsAwesome/Agravaine and a few other Series 4 characters.../@comment-5350801-20120815231736/@comment-4650675-20120824180843

You are right, I admit (the nickname Aggy was hilarious by the way!)! I've thought of some other theories as to why Uther may have agreed to keep Agravaine inside Camelot:
 * Uther may have thought that Agravaine would never try anything againist the king or prince.
 * Uther may have thought that Agravaine's love for her sister made him love Arthur,so even if he hated Uther he would never hurt his son.

However, it's a pity because Agravaine's introduction was poorly done, and we did not see Uther's reaction or thoughts on it (same for Morgana's betrayal, Guinevere taking care of him e.t.c.). I think Uther's reappearance on the show is a great chance to correct what was done badly in the past, in terms of scriptwriting!