The bus seen here is supposed to be for my American 1920's Adventurers, Trains, and Town layout, but it originally hails from the United Kingdom as the Associated Equipment Company (AEC) Regent mark III. It is related to the AEC Regent III RT, of which several buses were used as the basis for the Harry Potter "Knight Bus". This purple triple deck bus was then recreated in set 4755 and 4866, (both named the "Knight Bus") which provided the inspiration for this model.
The back features the entryway to the bus, along with a railing, rear bumper and single tail light.
The roof and upper level are removable and are even grouped individually in Lego Digital Designer to allow for easy access. Sadly, there are no stairs in the model, as I couldn't figure out how to make them fit inside.... sorry!