The man on the front row second from the right as you look at it looks like Rudyard Kipling
James
Well James, thanks for your help right at the beginning! You will see that gradually the identity of many other people present have been revealed... but we still don't know for sure where and what the event was, though we know it was taken between June 22 and July 7, most likely the weekend of July 1st/2nd.
Back to Rudyard: he was a major freemason, as were all the the men so far identified in the group: indeed the Duke of Connaught was a grand master. Lots of the people in the photo worked on the Imperial War Graves Commission, as did Kipling. He founded "The Builders of the Silent Cities Lodge No 12" in St Omer, France, in January 1922, a condition of membership being a connection with the IWGC.
I know very little about the freemasons, especially where to find archives: but perhaps they organised an equestrian event, followed by a lodge lunch?
Paddy