I totally buy into him being traumatised by his mother's death. He did have to share his mourning and loss with the world, his mother wasn't just his to grieve. Since her death there have been conspiracy theories about the accident, publicised annual reports be it birth day or death anniversary, he can't truly escape her death.
Doesn't matter that William has apparently coped, everyone deals with emotions and trauma individually. I can understand that becoming a husband and father would resurface pain and fear that he may have put aside.
But I have issue with him using Diana's death as his USP. I'm not convinced he's triggered by London, he's happily lived there all his life - he might feel it's chaotic but triggering because of his mum? I feel that's just another reason for him to hate England. He's also happily visited Paris for rugby didn't the city where his mother died trigger him? The guy needs a therapist without any agenda except to help him.