David Hartley was descended from an inventor who had built himself a fireproof house. And Hartley decided that the best way to get people interested in this invention was to show just how safe the house was.
He invited the king and queen to breakfast, and while they ate in one room of the house, he set a fire in the room underneath - burning up all sorts of inflammable materials. He even lit overenthusiastic fires on the staircases - despite the fact that the staircases were made of ordinary materials!
Fortunately for Hartley, the Fire-Proof House turned out to be just fire-proof enough, and the king and queen finished their breakfast in peace.