The unpleasant comments here are aimed towards one royal in particular, please start a separate thread elsewhere!
Just remembered this book, partly about Charles being a terrible guest (don't know how true it is though):
"In his book, Tom Bowers reveals that Charles sends his staff ahead a day early with a truck carrying furniture to replace the perfectly appropriate fittings in the billionaire homes' guest rooms. And not just the odd chest of drawers: the truck containes nothing less than Charles and Camilla’s complete bedrooms, including the Prince’s orthopaedic bed, along with his own linen.
His staff had also makes sure to pack a small radio, Charles’s own lavatory seat, rolls of Kleenex Premium Comfort lavatory paper, Laphroaig whisky and bottled water (for both bedrooms), plus two landscapes of the Scottish Highlands. He screamed at seeing an unsightly object on his food until Camilla assured him 'Darling, it is Cling Wrap". He grabbed an entire loaf of Italian bread from a formal dining table from a billionaire reaching for it claiming it was his bread, and only eats his own food — organic, of course. He has been known to cancel these elaborately staged weekend parties at a moment's notice because: "He had felt unable to abandon the beauty of his sunlit garden at Highgrove.'" The Queen had to intervene at one point as Charles was snubbing Carole Middleton at social events.
And he is never without his flask of specially mixed martinis poured by his aide. He hates traveling on commercial airlines and Camilla has developed the same spoiled lifestyle tastes."