Who is the most important character in "The Canterville Ghost" and why?

This is an opinion question, so feel free to state any character from the story.  The important part is adequately defending your answer.  The explanation for your choice should be more in depth than a single reason.  
For example, I could claim that the most important character is Lord Canterville. He is the most important character because he sold the haunted house to the Otis family.  If he didn't sell the house, there wouldn't be a story.  That's the only reason I can come up with though, so Lord Canterville is probably not a good choice.  
I would go with Virginia or Sir Simon for the most important character.  If I was forced to choose between the two, I would go with Sir Simon.  He gets more page time, so he is an easier choice to defend because there's more information to use.  Additionally, he is a deeper and more dynamic character than Virginia.  Virginia is super important because without her Sir Simon is still forever doomed to haunt the mansion, but Virginia doesn't quite shape events of the story as powerfully as the ghost.  If Sir Simon wasn't in the story, Virginia's help wouldn't be necessary anyway.  Sir Simon propels the story forward as he tries to antagonize just about everybody in the house, and he fails every single time.  We see him go through a range of emotions during that time too.  We see him angry, scared, and sad.  Readers really get to know Sir Simon, his motivations, and his emotions.  Virginia, on the other hand, stays a mystery.  Even her own husband can't get her to explain how she helped the ghost.  Sir Simon is definitely the character that I feel is most important to the story.