Yes Steve diesel it is.
I was driving past our local Oxfam shop when i spotted this so turned around to take a closer look as you do.The owner came out as i was taking the photo,s so got to talking.A nice chap ex army that took a hit in Bosnia i think he said.Anyway the bike is an ex Russian ammunition carrier from 1946 which he now uses to fetch and carry bike amongst other things,said he got stopped by plod with 1/2 tonne of building sand on there once.The engine is an 1100cc from a fork truck with belt drive.He also has in his collection a diesel Enfield.
Regards
Alan