I understand that fox attacks on cats are very rare. I'm thinking that the average fox wouldn't want his good looks spoiled by cat claws! I also wonder whether there isn't an element of pecking order going on as well. The cat and fox commonly roll up together at teatime, the cat campaigning by pawing at the back door while he waits patiently a few feet away behind. He sees that the cat is allowed in, a much more privileged situation than he's allowed to enjoy, she comes when called and gets patted, etc., unlike him. "He knows his place," sort of thing. Or maybe I'm just talking daft...