---
title: "Donald McLachlan"
type: "entity"
entity_kind: "person"
status: "hub"
canonical_name: "Donald McLachlan"
aliases: []
first_seen: "2026-09-23T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["Room 39 (1968)","Naval Intelligence Division","John Godfrey","Admiralty Code origin","institutional history of British naval intelligence"]
seek_code_commit: "0158402"
---


Journalist and author of *Room 39: A Study in Naval Intelligence* (1968), the institutional history of the British Admiralty's Naval Intelligence Division that is the primary source behind [[claim-godfrey-1939-devised-admiralty-codes-two-axis-grading-to-fix-report-anarchy|John Godfrey's 1939 origination of the Admiralty Code's two-axis grading system]].

He matters to this vault as the unread primary anchoring a load-bearing claim: the vault currently knows his account only secondhand, through Ludo Block's 2021 retelling, and *Room 39* itself is access-restricted (controlled lending on archive.org) — the gap that [[question-verify-godfrey-nid-origin-against-mclachlan-room-39]] exists to close.

## References
- [[claim-godfrey-1939-devised-admiralty-codes-two-axis-grading-to-fix-report-anarchy]] — the claim resting on his account.
- [[observation-admiralty-code-diplomatics-independent-origin-not-shared-descent]] — the synthesis that also rests on his account, secondhand.
- [[question-verify-godfrey-nid-origin-against-mclachlan-room-39]] — the open verification against his primary text.

- 2026-09-24: Of Block's account, only "intolerable" (p. 22) and two long passages from an unnamed officer (p. 23) are McLachlan's own text; the p. 23 passage uses an "E" grade ([[claim-block-2021-attributes-only-intolerable-to-mclachlan-room-39-p22]], [[claim-block-2021-quoted-mclachlan-passage-uses-grade-e-against-a-to-d-scale]]). RMG holds Godfrey–McLachlan correspondence on writing the book (rmg.co.uk/collections/archive/rmgc-object-478556), unopened.