I too believe this is very exceptional.
I have asked around all the avid fly fishos I know and they are pretty stunned. I was wondering if the African species which this seems to be (trachinotus africanus), might have slightly different habits (??) but I can't find anyone to agree with that explanation! Fishbase lists the food items of this species as molluscs and crabs.
Having witnessed this first hand, I can say that the permit seem to be feeding upon a truly VAST sardine ball, hanging low along with diamond trevally and golden trevally, while queenfish, bonito, barracuda etc patrol the top of the ball. Sub-surface stickbaits matching the size of the sardines seemed to be most effective (as they were with the trevally species), but as one of Ed's pictures shows, one even came up and took a popper.
I can also say that it is a most strange fish to catch! The strike feels like you have a hit a snag - absolutely rock solid - and just when you think the fight is over and the fish is coming to the net, be prepared to for a lot more action to erupt. They really do not like coming up to the surface. Superb value.