A week ago I made a cup of tea. It had the unmissable taint of formic acid, the pungent signature of the ant. Undrinkable of course. I suspected a stray ant in the teapot. Cut to yesterday afternoon,  I heat the kettle for tepid water to make bread, and along with the 450ml of aqua out comes a dozen ants. Pour out the rest of the water, more ants. Refill and tip, more ants. A series of a dozen refills and each emptying delivers yet more ants. Here you can see one of the last,  washed out at rinse number 17.

Hell, an ant nest in the kettle? Is this like Jonestown for Ants? Was some errant ant leader simply suicidal. Is it an ant cult? More filling and emptying, and while the ants have gone the smell of formic acid remains.  How long had they been there, perhaps their bodies disguised as tea leaves in the teapot?
Post Script: Hunting for an antidote to that persisent formic smell, I've boiled kettle water with a chunk of lemon, twice, then followed up with water and vinegar, ( yes, same citric acid trick).The inside of the kettle is, improved, shiny eve, and the smell, well the best I can say is ameliorated.