Or, for that matter, any other film.
From the comment section.
Gofipro wrote:
Random find. This is how Brits promote a film: Promotion for the DVD film release of Lady Godiva and sponsored charity ride. Rotten Row, Hyde Park, London, Britain – 19 May 2008

Damn, I live five minutes walk from there… if only someone had told me!
I wonder if all of them are experienced riders. I’d think at least some experience is needed to confidently ride a horse naked.