If this is indeed the bus I think it is it started life in January 1929 as Hants & Dorset Fleet No. 268, a Leyland Lion registered RU 8678.
In later life it served as a mobile shop at car events for the book/car spares shop "The Complete Automobilist" in the 1970's before eventually being rescued and having a 'spare' restored ex-Ribble Leyland body fitted to it by Dougie and Ross Scoular in 2007. It now resides in the Scottish Bus Museum.
If it's not that bus then for the moment I have idea what else it could be!