A cache of wartime papers signed by Alan Turing sold at a London auction for nearly $500,000. The documents, dubbed the “Bayley papers,” reveal details of a secret voice‑encryption effort called Delilah, built between 1943 and 1945. They include Turing’s handwritten notes and assistant Donald Bayley’s annotations, shedding light on a little‑known engineering side of the pioneer and provide rare insight into wartime hardware development.

During the war Turing moved from abstract mathematics to hands‑on electronics, setting up a bench in a Nissen hut at Hanslope Park – now the secret His Majesty’s Government Communications Centre. Inspired by Bell Labs’ massive SIGSALY system, he and Bayley miniaturized speech encryption into three shoebox‑sized units weighing a total of 39 kg, portable enough for field deployment.

Bayley kept the notebooks until his death in 2020, allowing the British government to intervene and block export, insisting a UK buyer should own the material as part of the national story. The release confirms Turing’s role in early secure voice communications, a precursor to global modern encrypted radio for intelligence and secure today digital VoIP network protocols.