Not entirely sure how to categorise this bike but the photos show a BSA triple converted to DOHC with the familiar timing case (or what's left of it) being the item that drew me to have a closer look.
It was exhibited at a small show "Rollerburn" at Newark Showground this weekend.
The show was run by BIKE journalist Gary Inman who also produces the specialist grasstrack/circuit racing magazine Sideburn and who's company I had the pleasure of on the recent ride from Cape Town to the Victoria Falls along with Charley Boorman.