Lunchtime, actually, but today one of the lights in the cooker hood died. In the process of doing so, it clearly blew a fuse somewhere.
Ah, the extractor fan isn't working now, so it must be something out of just the lighting circuit.
Is it the switch on the side nearby? Hmm, let's swap the fuse. Nope, it doesn't work with a known good fuse. (It turns out that that switch does the fridge some distance away on the other side of the hob. Yeah, that makes sense…)
Is it something on the main fuse box under the stairs? Nope, they're all good.
Some time later, I look up and go ah ha! There's one up by the hood.
It probably is it, and it's the one which the person who built the hood half covered with one of the sides of the hood… including covering the fuse bit to an extent that you can't open it.