Jon Allen has been a practising architect for twenty-five years. He has worked closely with Keith Critchlow, a world authority on geometry, and has developed a particular interest in the application of geometry in architectural design. He lives in London. He is also the author of Making Geometry (Floris Books, 2012). Professor Keith Critchlow is a well-known lecturer and author. He is a founder member of RILKO (Research Into Lost Knowledge Organisation), a founder member and Director of Studies of Kairos and a founder member and President of the Temenos Academy. He has been a senior lecturer at the Architectural Association in London and has taught Islamic Art at the Royal College of Art; he now lectures worldwide on architecture and sacred geometry. His many previous books include Order in Space, Islamic Patterns: An Analytical and Cosmological Approach, Markings: Aerial Views of Sacred Landscapes, and Soul as Sphere and Androgyne.