Yes, it turns out to be eosinophilic keratitis potentially associated with feline herpes and the cat doesn't normally experience any discomfort which explains why he is a bit miffed by all the attention. He's on a couple of different eye drops and a human antiviral drug for another fortnight. Have been told it may recur (like chicken pox/shingles) although, now they know what it is, any future occurrence will just be a case of home treatment until it goes away. It appears to be a reversible condition in all cases, although Tigs managed to get an ulcer along with it. I'd still not rule out a fight triggering it due to the ulcer and some associated evidence of paggs, viz. notch in ear and loose tufts of fur.