I am so glad you were there at the moment of conception to be able to make such a statement.
An age for age photographic comparison would be great, if it wasn't just a major search through to find similar or disimilar pictures. In the majority of pictures (to me and many other Brits, as evidenced by ysbels experience) Harry looks like Hewitt, the only reason he has the same eye movements and mannerisms is by association. A child copies the most consistant people in it's life, so it stands to reason that both boys would have picked up their Charles traits from Charles.
It is not a case of wanting to think badly of Diana, but if she hadn't had any affairs until after a formal separation, we would not be in any doubt as to who Harry's father is! (And no I am not wanting to go there Elspeth, but you brought it up)