Standing in the nave of Ely cathedral when I was 14, I stopped listening to the guide saying how long and how high and started wondering how on earth ordinary human beings created sky-scraping, dizzyingly high buildings on which even the top-most parts were delicately decorated. How, why and for whom were my questions. For God, for personal redemption and to make a living are the answers to the last two of those, but the "how" was harder to fathom. In this lecture we meet the Master Masons who both designed the buildings and ran the site. They commanded everything whether it was sourcing the vast quantities of wood and stone, recruiting the workforce or knowing enough about their various trades to be able to create heaven on earth out the cacophony of thousands of chisels and hammers. These men were charismatic leaders, but they were continually checked by their fellow Master Masons in the interests of making a building as strong as possible - we only see their successes, after all. They were real people who got into trouble with the law, who occasionally cheated on contracts, who liked to start a job but not to finish it. On the other hand, their creations remain to this day, some breathtakingly beautiful in their exquisite detail causing us, centuries later, to stand in a nave and wonder.