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 was a well-known lecturer and author. He was 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 was Professor Emeritus and founder of the Visual Islamic and Traditional Arts Programme at the Royal College of Art, now the Prince's School of Traditional Arts. His many previous books include Order in Space, Islamic Patterns: An Analytical and Cosmological Approach, Markings: Aerial Views of Sacred Landscapes, Soul as Sphere and Androgyne, and Time Stands Still: New Light on Megalithic Science (Floris Books, 2007).