I finished my lunch (hey, I was hungry!), then called back. I suggested that she switch off all the circuit breakers, switch on the main trip switch, then turn the individual circuit breakers on one by one until one tripped a shutdown. Using this technique, the problem was soon isolated: it was the kettle.
I actually liked this kettle. Sure, it was metal, it was noisy and its lid didn't spring up very well, but it didn't slosh water everywhere when it poured. However, a recent clean to get rid of the limescale seems to have hurt it (which I dimly remember having happened to a kettle before) and today it shorted out, taking the rest of the house with it.
25 years ago, my maternal grandparents got us an electric kettle for our wedding. My wife isn't keen on it, as it has the element in contact with the water so it furs up a lot — oh, that and the fact that it doesn't turn itself off when it's boiled its contents. She probably doesn't like how it looks, either. Anyway, because of this it lives in the attic, only to appear on those rare occasions when the kettle we have dies.
So, today our kettle died, so I went to the attic and got down the 25-year-old one. Inside was the following note I'd left myself:
For those who don't want to try deciphering that, it says: "How long did the jug kettle last this time? 11/1/94"...