OMG, I'm absolutely shaking! I just heard some long, loud yowls, dashed outside, and there was Rufus on the front path FIGHTING with Frankie, the cat who lives three doors up. They were really grappling with each other, rolling around and kicking.

I had to break it up. They kept yowling at each other until Frankie beat a retreat - he was in Rufus' territory. And I'm absolutely shocked at the amount of fur there was in the front garden, handfuls and handfuls of it, only from Rufus. Now Rufus is a long-haired cat so it was mostly fluff, but I brushed him pretty thoroughly only last night and I can't believe how much more has come off him. He came indoors, still growling, and he seemed to be shaking (or was I imagining that because I was shaking?) He's had a cuddle, a few treats, has drunk some water and eaten some biscuits. He's let me inspect him and I can't see any injuries, thank goodness.
Now Rufus is a very laid-back cat, and Frankie is an old friend. He was friends with my beloved Blake, and he used to come into the house and sleep near Blake (Blake wasn't as keen on Frankie as Frankie was on Blake). I used to feed him when his humans were away, and they'd feed Blake when I was away. I have an arrangement with a different neighbour these days. Maybe that's just as well...

Frankie can't come into the house any more as Rufus has an electronic cat flap, so I don't often interact with him nowadays.
I think Frankie is ten or twelve, a mature cat, anyway, and Rufus is five. I can't understand why they've suddenly had a fight. As far as I know that's never happened before. I'm around most of the time and I don't sleep much, so I would have noticed a fight. I don't think there's anything I can do about it, as such (what, call them in and give them a serious talking to? Tell Frankie to apologise - as I said, he was on Rufus' patch - and make them shake paws?) but I've never experienced a cat fight before (yeah, I must have led a sheltered life) and I really do feel quite shaken. I'm really worried Rufus may get hurt.