Godfrey, as Director of the Naval Intelligence Division in 1939, had the Admiralty Code's source/information split devised to end 'the anarchy of different information reports'

intelligence-tradecraftadmiralty-codesource-evaluationhistoriographygodfreynaval-intelligenceunverified

John Godfrey became Director of the British Admiralty's Naval Intelligence Division (NID) in 1939 and, intolerant of "the anarchy of different information reports without a clear indication of their value," had a grading system devised that evaluated a report's source and its information content on two separate scales. Per Ludo Block's 2021 account, citing Donald McLachlan's 1968 institutional history Room 39: A Study in Naval Intelligence: "A simple system was devised in which the source and the information itself were evaluated separately, coding the evaluation with letters and numbers from 'A1' to 'D5'."

The original 1939 scale (A–D, 1–5) is narrower than the current NATO doctrine — A–F for source reliability, 1–6 for information credibility, codified as STANAG 2511 — which would mean the letter/number range widened at some point between 1939 and its modern codification, a detail not otherwise dated in the vault's existing Admiralty Code note. That widening inference rests on Block's own "A1 to D5" summary, which the McLachlan passage Block himself quotes complicates: an "E" grade appears in a wartime example (claim-block-2021-quoted-mclachlan-passage-uses-grade-e-against-a-to-d-scale), so the wartime scale may not have been the narrow A–D form at all.

[unverified-primary — needs direct read of Room 39 (1968), currently access-restricted]. See the open verification question.