The great cathedrals were the wonders of the medieval world. Many were the tallest structures on earth the highest buildings created since the pyramids and until the Eiffel Tower, yet they were built without any of the technological aids of the modern world and with little more than set-squares and dividers, ropes and pulleys, hammers and chisels. The vision was to create a sense of heaven on earth and the medieval cathedral aspired to be nothing less than “the new Jerusalem”. Spectacular effects were achieved as this ambition was realised leading to a revolution in design and a golden age for cathedral architecture in England. Who were the people who built them? What drove them? And just how were they able to build with such stupendous skill, vision and ambition? Architectural historian Jon Cannon, author of the recent, acclaimed Cathedral, goes in search of the clues that shed light on how our medieval forebears were able to realise such bold ambition. From the fan vaulting at Gloucester to the stained glass at York, from the solid mass of Norwich to the soaring elegance of the Octagon at Ely, Jon climbs up above the stone vaulted ceilings, along the parapets, through the roof voids and down into the crypts of the greatest cathedrals to find out how, and why, it was done.