Just aas an aside - and apologies in advance if I upset you rainboe - I was once boarding a flight in Greece, via steps (front and back) while the aircraft was being refuelled. Cabin crew in the doorway, cant remember seeing any refuelers acting in a "supervisory" way - but I
DID notice another passenger further back in the queue
SMOKING on the way to the aircraft steps
(I guess the "smoking is permitted once outside the terminal" message kind of got mixed up!) - Anyhow, I mentioned it to the FA once at the top of the steps, and she dealt with it very professionally, a load bellow to the effect of
"PUT THAT CIGARETTE OUT NOW!" followed by a few quiet words of explination on boarding seemed to do the trick.