This was taken today at Wrest Park (Bedfordshire) at the English Heritage's St. George's Day weekend.
The gentleman is representing a (19th Century) Colonel of Skinner's Horse, the Yellow Boys.
He was busy talking with a photojournalist (with a lens that looked more like a weapon of mass destruction!) so I grabbed a quick shot; there were kids around him in 21st century clothing, hence the above waist shot.