So I went to the little sandwich van that comes around work. I did buy a sandwich (210 calories!) and then I really thought about it. This is a heavyish feeling sandwich. It isn't made by the person who drives the van and is company owned but I feel they probably have it delivered to them from a third party.
I checked that the packaging didn't say "210cals per 100g" (it would be more accurate!).
The bread alone, based on the average for two slices of bread, would be about 210 calories... So... Is the filling completely calorie free? Cheese ham mustard and mayo?! I think not! I've no idea how many calories is actually in it now. But I'm shocked at how inaccurate it is. In future I'll use a bit more common sense and stick to the salad!