In my opinion it's a gross invasion of privacy. It's fairly clear from the above photo that the Duchess couldn't have been seen from the road with the naked eye. This wasn't a case of some z-list 'celebrity' wandering down a beach on the coast of California with her tits out, it's the case of a young couple relaxing in what I imagine they thought was the comfort and security of a holiday villa. If they were a random yuppie couple we'd be talking about voyeurism and about exactly what sort of pervert camps out half a mile from someone's house with a telephoto lens in the hope someone takes their top off.