Sadly, it dropped the wireless connection later, and hasn't managed to keep it alive for more than about 20 minutes at a time since. After much research on the web, I found that there is a "known bug" with the Belkin modem/router/wireless access point that I've bought. Lots of people offer lots of "worked for me" fixes, but none of them did it in this case.
One problem seems to be that Anna connects to a VPN during the working day. That shouldn't matter, but the device doesn't see it that way. The office machine is connected to the VPN, the laptop via WiFi should be to the Internet itself, but doesn't work at all.
And even when the VPN is "off" and the office machine working the internet normally, the wireless signal drops with alarming regularity.
So I'm bidding on a separate wireless access point and will disable the Belkin one. Mutter!