You might have noticed the server was offline for a few days.
The fibre modem that connects it to the internet suffered a violent component failure, with the magic smoke and burn marks you'd expect. We had to get a technician out to replace the modem, which has now been done.
No data was lost and things should be continuing as normal! Hurrah!
Thanks for letting us know what was going on. I was worried for the moment of downtime.