So there are 2 distinct points of view here.
Positive: Dukes turn around struggling school, great experience of teaching and environment, don't believe it's private equity funded, management very open. Funding structure not paramount, "small nurturing charitable" ventures can also have sub-optimal results.
Negative: Dukes is funded by "vampire squid banks", "the story he spins", "he WILL sell in a few years", "command higher fees", "classic PE company and profits will always be first", "escaping taxes", "no parents at my PR firm send their kids there".
While the factual truth about funding is likely in the middle (Dukes likely use a range of funding sources), I'm astonished by the language of the negative reviews. Epithets that come to mind are vociferous, spiteful, scaremongering. It puts me off when contributors have to resort to this tactic.
Devonshire House is a large school of its kind. If anyone actively involved, parents or teachers, have had an awful experience pre or post Dukes, during or after their involvement, I am waiting to hear from them. So far, the only first hand experiences I've heard are positive. They align with my own experiences, and therefore I am absolutely delighted to send my own children there.