Where Industrial Strength Computer Science Began
When I graduated in 1967, the mechanical analog products of Alexander Graham Bell and Almond B. Strowger were still in production at Plessey factories in Liverpool and Beeston. Soon, I found myself flying to meetings at these factories and visiting Taplow Court near London Airport, where researchers and project managers worked. The strategic corporate investment planned an Industrial Strength Computer with decades of software reliability for the global communications industry. It led to the fault-tolerant computer known as PP250. Ever since the disclosure in 1972, this computer remains the archetype for capability-based digital-computers as the vital starting point for Industrial Strength Computer Science. Industrial Strength Computer Science demands Capability Limited Addressing governed by the laws of λ-calculus found in the Church-Turing Thesis.
 A.G. Bell and A.B. Strowger patented the telephone and the automatic telephone switch in 1876 and 1891 respectively.
 Capability-Based Computer Systems by Henry M. Levy, published by Digital Press in 1984, remains the best comprehensive survey capability-based hardware and software systems. Visit https://homes.cs.washington.edu/~levy/capabook/
 Four papers published at the International Conference on Computer Communications (ICCC), October 24-26, 1972 in Washington D. C. including Fault Resistance and Recovery within System 250. ICCC USA 10.1972
 The Church-Turing Thesis conjectures the equivalence between functions algorithmically computed by Turing Machines, the λ-calculus and humans.