From the article in the ‘links’ section, 1880.
This is how he spotted the barrow:
“Most of the members of the Society, being in carriages, kept to the roads. I was on horseback, and in taking a short cut through Buckholt Wood, with my mind intent on archaeology, I suddenly saw before me a huge mound! I rode to the top of it, and around it, and after a careful examiniation, came to the conclusion that it was a Long Barrow, and a very perfect one. Before many hours were past, in fact before I returned home that night, I had obtained permission, through the kindness of Lady Cromie and Mr. W.F. Beach, to have it opened and examined, and had also obtained [...] promises of funds sufficient to commence the work.”
Image credit: G B Witts
That's brilliant, not seen these diagrams before. It's probably my favourite Cotswolds site, shame it gets ridden on by mountain bikes but they're following in Witts' hoofprints!