Historical BBC documentary that depicts the work of codebreaker Gordon Welchman. During the Second World War, Welchman worked alongside Alan Turing at Bletchley Park, breaking German ciphers, and played a key role in cracking the Enigma machine. Following the war he moved to the United States and, after retiring, released a book detailing his work for both the US and UK military which led to him being ostracised by the National Security Agency.

Originally published in 1950 and written by the renowned mathematician, university professor, author and World War II codebreaker W. Gordon Welchman (1906-85), this textbook contains a treatment of projective geometry and provides a solid introduction to similar studies in space of more than two dimensions. The first three chapters analyse and establish the necessary foundations of the subject, whilst the remaining chapters are primarily concerned with the theory of conics, engaging with more complex topics such as metrical geometry, the application of matrix algebra, and invariants and covariants. The book also places much emphasis on the application of techniques rather than on the elementary principles of the subject and this is made easier by using algebraic foundations rather than purely geometrical axioms. This informative and insightful book will be of considerable value to scholars of mathematics as well as to anyone with an interest in the history of education.