> the first one to be given the official title of chief mouser by the British government was Larry in 2011

The Wikipedia article is obviously in error. It’s clear to me that the government serves Larry and at his convenience.

I was hoping that I wasn't getting my news from HN for a moment there.

British politicians are notorious sloppy eaters, lots of crumbs to be had.

Bear in mind that it's of Georgian construction and Grade 1 listed (so not just a façade), so there is presumably plenty of wood and plaster in its construction with corresponding voids. With humans comes food morsels. Some of the rooms offer doors onto the garden. Mice seem inevitable in those circumstances.

There's a mouse problem in the whole city. But then there's a mouse/rat problem in more or less any city of similar population density.