Cappy hasn't eaten in two days - so today I introduced food again. 4 bites in the morning, 8 bites in the afternoon and had a bowl full of one chicken breast this even.
Bastard wouldn't even consider it until I mixed in some of his raw food. Then he ate quite happily.
We haven't worked out what is wrong with him but it is most likely
3. Undiagnosed bug
I am going to do what I can not to operate on him needlessly but if it is what he wants to eat, it is what he will get.