There has never been any lead in a pencil. The black stuff found at Borrowdale, in the Lake District, in the sixteenth century looked enough like lead ore that people called it black lead, and it got a name of its own only in 1789, when the geologist Abraham Werner took one from the Greek for “to write”. Borrowdale’s was pure enough to saw into sticks, and valuable enough that in 1752 Parliament made stealing it a felony; later the miners were searched at the end of every shift.

Then Britain and France went to war, and France could not buy any. In 1794 the war minister, Lazare Carnot, asked Nicolas-Jacques Conté for a pencil that needed no English graphite. Conté ground up poorer graphite, mixed it with clay and baked it, and found that the more clay he added, the harder the point and the paler the line.

So the H and the B on the side of a pencil, the whole run from a draftsman’s 4H to an artist’s soft 8B, come out of a blockade. The best graphite in the world made one kind of pencil. Having none of it made all the others.