John Tiltman joined the British Army in 1914, saw service at the front during the Great War, and was wounded in France. In the period from 1921-29, he served with the Indian Army as a cryptanalyst.

After a decade as a War Office civilian at the Government Code and Cypher School (GC&CS), the interwar cryptologic organization, John was recalled to active duty. His experience enabled him to assist in many areas of endeavor at GC&CS. Considered one of Bletchley Park's finest cryptanalysts on non-machine systems, he also had an important role in solving the German TUNNY machine system.

John Tiltman was an early and persistent advocate of British cooperation with the United States in cryptology. His advocacy helped achieve smooth relations during World War II.

In 1944, he was promoted to Brigadier and appointed Deputy Director of GC&CS. He continued in 1946, as Assistant Director of the Government Communications Headquarters (GCHQ), successor to GC&CS.

John Tiltman became Senior GCHQ Liaison Officer at the Army Security Agency in 1949.

After reaching normal retirement age, he was retained by GCHQ from 1954-1964. From 1964-1980 he was a consultant and researcher at NSA, spending in all 60 years at the cutting edge of SIGINT.

John Tiltman made the transition from the manual ciphers of the early 20th century to the sophisticated machine systems of the latter half of the century. "The Brig," as he was affectionately known in both countries, compiled a lengthy record of high achievement. His efforts at training and his attention to all the many facets that make up cryptology inspired the best in all who encountered him.

Brigadier John Tiltman died in August 1982.