Regina had been proud of the success they had had with her own weaving experiments back on her farmstead, but all they had been able to produce was coarse cloth. This loom design had come from another of the experts Artorius had gathered up in his sweeps across the countryside, and the results were far better.

She passed a little time with old Marina. Marina liked to talk of old times in Verulamium, and Regina knew that the skill and loyalty of her granddaughter had been a great comfort to Marina since the death of poor Carausias a few winters before. But Regina escaped before Marina produced her foul-smelling buckets and asked her to contribute. Marina’s vegetable dyes needed a fixing agent, and the best fixer of all was stale urine: a vintage half a month old was generally thought to be just right.

Regina made more marks on her wax tablet, and moved on.

Of all the industries that had sprouted here on the dunon’s plateau, the most significant was iron: fully half the manufactory area of the plateau was given over to its complex production. Myrddin ruled his little empire of iron and fire and charcoal as if he were king of the underworld. As she approached the forges, two of Myrddin’s helpers—unfree, recent arrivals both of them—were working on a charcoal clamp. Myrddin insisted on training up his clamp workers personally, and from the look of the hollow, sleepless eyes of these two men, his training regime had been as brutal and unrelenting as ever.

This clamp was a few days old and several paces across. A mound of timber had been covered with a thick layer of damp leaves and bracken, turf, and soil. Fire had been started inside with embers poured into a hole in the top, and then the mound was capped off, so that the wood within could only consume itself. Running the clamp was a skilled job. A constant watch had to be kept on it by day and night, for as the wood turned to charcoal it would shrink, and the clamp could collapse on itself—and if air got in the whole thing would go up in an unproductive blaze. When the burning was done the mound had to be dismantled carefully, and the charcoal doused with water, for while hot it had a tendency to erupt into flames spontaneously. There were many such clamps, some much larger, in operation day and night beyond the hill fort, for Myrddin’s works demanded a constant and heavy supply of charcoal. You could smelt some metal ores with wood fires, but only charcoal could provide the high temperatures needed for iron.