Harry didn't mean to fall in love with him, and he especially didn't /want/ to fall in love with him, but it happened. When he sees the engagement ring on Louis' finger, he feels as if the world has stopped. Harry does what he has to do, but he's not the type of boy who should be rhudely barging in on a white veil occasion. But then again, Louis is not the type of boy who should be marrying the wrong girl.