I think that MM is treating this visit as if she were performing in a film! Give a good performance then who knows what may eminate from it in tinslel town who are bound to be watching, a bad or inadequate performance then further 'shows' could be in short supply! P. H has obviously been trained to play his role in all this, and a seemingly bad performance will earn him the wrath of his puppet master!
I guess Archie was left at home as MM doesn't want him to have anything to do with his paternal family, simple as that! I have a feeling that Doria has also been part of this show, perhaps being used or perhaps a willing participant? who knows?!!
If perhaps P.H feels that this behaviour towards the Queen and his father is payback time for their treatment of his mother, then sadly the only person he is really hurting here is his brother and his family. The Queen, is nearing the end of her life, PC may not be King for that long as he too is not a young man, but William will have to pick up the rein:-)s and steer the RF through what could be stormy times. Why on earth would you want to hurt the very person you have always purported to love and with whom you shared that mother and who had nothing to do with her death?!