Was just randomly mooching about my system and noticed that my server backup has been failing every day for the last 6 and a half weeks.

Have fixed the problem - somehow I'd buggered the aws CLI, I don't know how. It's running now. Amazing that what I didn't know about didn't stress me.

So now going to add some logging/alerting to the end of that backup script, that of course should have been there all along.

Check your backups!