Rather annoyingly I came home to fairly dead internet connection.
Some investigation revealed that it was only partially dead, and was serving external requests without trauma. To check things I had to log into the router, and owing to the joke that is any Java application the only way in was telnetting into the glorious Cisco command line. It's really a joy to behold. Cisco's marketing strategy is to make great products but make them so completely god awful to use that you need to do a two grand training course to configure them properly.
What was strange is that once Dave has beaten his head against the wall for about three days and got this router correctly configured it just doesn't miss a beat.
Sure enough, that proved to be the case this time, and with some clever remote logins Dave diagnosed DNS issues with the ISP.
Switching to an alternate remedied the problem, and hence I can post again - yey!