In the autumn of 1941 the thing holding up codebreaking at Bletchley Park was not the mathematics. It was staff. On 21 October 1941 four of the people doing the work wrote directly to Winston Churchill, over the heads of their own management, to say so. The letter and the Prime Minister's reply survive together at The National Archives at Kew, in a file numbered HW 1/155. The catalogue entry for it is one flat line: "Request for more staff sent to PM, response and action taken Nov 18".
Key Takeaways
- Four codebreakers signed the letter on 21 October 1941: A M Turing, W G Welchman, C H O'D Alexander and P S Milner-Barry. It is headed "Secret and Confidential / Prime Minister only".
- Their three named bottlenecks were small and specific: about twenty untrained women clerks, about twenty trained typists, and a detachment of the Women's Royal Naval Service to test machine output, promised in July and still not there by late October.
- One delay they reported was that a machine room had stopped working night shifts, pushing the finding of the naval keys back "at least twelve hours every day".
- Churchill's minute the next day, carrying a red "Action This Day" sticker, told General Ismay, his chief military adviser: "Make sure they have all they want on extreme priority and report to me that this has been done."
- Ismay's reply names the levers he pulled: the Ministry of Labour, and the Admiralty department dealing with the WRNS.
What did the Bletchley Park codebreakers actually ask for?
Almost nothing, by the standards of a world war. That is the point the four signatories press hardest.
The letter is headed "Hut 6 and Hut 8". The National Archives glosses those as the sections dealing with Army and Air Force Enigma, and with Naval Enigma; the letter's own section headings, quoted in the table below, say "Military and Air Force Enigma" for the same hut. It opens by reminding the Prime Minister of a recent visit, which The National Archives dates to September 1941: "Some weeks ago you paid us the honour of a visit, and we believe that you regard our work as important."
Then it gets specific. Three numbered complaints, each with a price tag you could pay out of petty cash.
| The ask |
The stated reason, in the letter's words |
Its section heading |
| About twenty more untrained Grade III women clerks |
The Hollerith section under Mr Freeborn "has had to stop working night shifts", so "the finding of the naval keys is being delayed at least twelve hours every day" |
Breaking of Naval Enigma (Hut 8) |
| About twenty trained typists |
Intercepted Middle East wireless traffic cannot all be decoded, for "shortage of trained typists ... and the fatigue of our present decoding staff"; "this has been the state of affairs since May" |
Military and Air Force Enigma (Hut 6) |
| A detachment of the WRNS |
Promised in July that the WRNS would take over "the testing of the 'stories' produced by the bombes"; by late October, "nothing has been done" |
Bombe testing, Hut 6 and Hut 8 |
Two details in that table repay a second look.
The first is the word "stories", which is what the letter calls the output the machines threw up for checking. The second is that the third complaint is deliberately ranked lowest. The four say so outright, because the missing WRNS had not actually stopped anything going out of the door. It had simply meant that people needed elsewhere were doing the testing themselves.
A further worry rides along with the first complaint. Skilled men, in the letter's words "both with the British Tabulating Company at Letchworth and in Freeborn's section here", had been exempt from military service and were now liable to call-up. The catalogue gives that firm its full name, the British Tabulating Machine Company Ltd; the letter drops the middle word. A separate file, covering June 1942 to September 1943 and so describing a later period than the letter, records that the same company produced both the bombes and the Hollerith tabulating equipment.
Twenty typists is a startlingly small thing to stand between an army and its enemy's radio traffic, and it is a reminder that most of the labour in codebreaking has always been transcription rather than insight. If you have ever ground through a daily cryptogram letter by letter, you have done the shape of that work.
A fourth section is a general one. There were other obstacles, some of them contentious, which the four decline to set out in full.
Why did they write to the Prime Minister at all?
Because everything else had been tried. The letter says so plainly, and it is the sentence that makes the document unusual rather than merely detailed:
Our reason for writing to you direct is that for months we have done everything that we possibly can through the normal channels, and that we despair of any early improvement without your intervention.
The catalogue corroborates that there really were normal channels, and that they had been busy. The file covering September 1941, the month before the letter, is described as holding a directorate paper on staff problems at Bletchley Park, "particularly recruiting and pay", along with "Hut 6 problems as presented to EWT by G Welchman" and the grading and pay of staff generally. The catalogue leaves those initials unexpanded, and so, deliberately, does this article: no record consulted for it says who EWT was. That file is HW 14/19. A later file in the same series, from March 1942, identifies Welchman without ceremony as "Head of Hut 6".
The four are also careful about who they are not blaming. The letter praises Commander Travis by name for the supply of machines, and closes the argument with a disclaimer: "We have written this letter entirely on our own initiative. We do not know who or what is responsible for our difficulties, and most emphatically we do not want to be taken as criticising Commander Travis who has all along done his utmost to help us in every possible way."
It is signed, in the formula of the period, "We are, Sir, Your obedient servants".
How did the letter get from Bletchley Park to Downing Street?
By train and taxi. Bletchley Park's output already had a route to the Prime Minister's desk: the archive series the letter sits in holds signals intelligence summaries sent by the head of MI6, known as "C", to the Prime Minister in batches several times a day, under the code name BONIFACE. That channel was for intelligence. It was not a channel for complaining about typists.
So Milner-Barry carried the letter himself. Writing in 1986 in the journal Intelligence and National Security, he could not recall why he had been chosen, and guessed it was "because I was the most readily expendable from the scene of action". His account of the trip is the best-known passage in the whole episode:
What I do recall is arriving at Euston Station, hailing a taxi, and with a sense of total incredulity (can this really be happening?) inviting the driver to take me to 10 Downing Street. The taxi-driver never blinked an eyelid.
At the entrance to Downing Street he found "just a wooden barrier across the road, and one uniformed policeman who waved my driver on". He did not meet Churchill. He handed the letter to a figure he later identified as Brigadier Harvie-Watt, the Prime Minister's parliamentary private secretary, who promised to deliver it and stress its urgency. Then he took the next train back.
He also records the reaction at home. Meeting Commander Denniston in a corridor some days later, he was met with "some rather wry remark about our unorthodox behaviour", though Denniston "was much too nice a man to bear malice". The National Archives puts it less gently: the episode caused tensions at Bletchley Park, and the four signatories were dubbed the "wicked uncles".
What did Churchill do about it?
He wrote a minute the next day, 22 October 1941, to General Ismay, his chief military adviser. The note carries a red "Action This Day" sticker. It reads:
Make sure they have all they want on extreme priority and report to me that this has been done.
That is the wording The National Archives gives from the file itself. Published renderings differ by a single word: the version printed in the collected Turing writings ends "report to me that this had been done". The difference changes nothing about the instruction, but a reader comparing two books should not conclude that one of them has invented a document.
The more informative half of the exchange is Ismay's reply, dated 18 November 1941 and headed from the Office of the Minister of Defence. It names the two doors he knocked on:
On the receipt of your minute at Flag 'A', I immediately got into touch with the Ministry of Labour and the Department of the Admiralty which deals with W.R.N.S., and gave instructions that the staff requirements at Bletchley Park should be given extreme priority.
He then reports: "Brigadier Menzies has now reported that the supply of labour for Bletchley in [sic] being very rapidly met. He adds that it is not entirely completed, but that he is satisfied that every possible measure is being taken." Menzies was the head of MI6, the same "C" whose office fed the daily intelligence to Churchill's desk. That November date is why the catalogue entry for a file dated 21 October runs on to "action taken Nov 18".
Two notes on that quotation, flagged for the same reason the has-or-had variance above is. The "in" where the sense wants "is" appears in the transcript as published. And the same page's summary paragraph renders the phrase "being very rapidly set" where its transcript panel reads "met". The two renderings disagree; the sense is not in doubt either way. A reader checking the wording should know which version they are looking at.
The sequence, September 1941 to January 1942
| Date |
What happened |
Where the record is |
| September 1941 |
Churchill visits Bletchley Park |
The National Archives, on HW 1/155 |
| September 1941 |
Directorate paper on staff problems, recruiting and pay; Hut 6's problems presented by Welchman |
The National Archives, HW 14/19 |
| 21 October 1941 |
The four sign the letter, marked "Prime Minister only"; Milner-Barry hand-delivers it to 10 Downing Street |
HW 1/155 |
| 22 October 1941 |
Churchill minutes General Ismay; the note carries a red "Action This Day" sticker |
HW 1/155 |
| 18 November 1941 |
Ismay reports back: Ministry of Labour and the Admiralty contacted, supply being very rapidly met but "not entirely completed" |
HW 1/155 |
| 1 to 15 January 1942 |
Staff strength for December 1941 recorded; four Buckinghamshire properties requisitioned for WRNS accommodation |
The National Archives, HW 14/26 |
What the record settles, and what it does not
It settles the ask, the answer and the follow-up, because all three sit in one file.
It does not settle the arithmetic of what changed. Three cautions are worth carrying.
The catalogue entry for the September 1941 directorate file records a WRNS complement for Hut 11, the bombe hut, totalling 220. That sits oddly beside a letter written the following month saying the WRNS promised for testing had not materialised. A complement on paper and operators actually detailed to a task are different things, and the catalogue description does not reconcile them. Neither does the letter.
The January 1942 file in the same series records four properties in Buckinghamshire being requisitioned for WRNS accommodation, alongside a case for expanding the wider signals intelligence organisation that the Chiefs of Staff Committee put into effect. That is the right kind of thing to follow from an "extreme priority" instruction. The catalogue entry does not say it did, and neither does anything quoted here.
And Milner-Barry's often-quoted line that "almost from that day the rough ways began miraculously to be made smooth" is a recollection published forty-five years afterwards, written by a man who had only just seen the Prime Minister's minute for the first time. He is explicit about that: "It was some forty years later before I found out what happened to that letter."
HW 1/155 is open, but it has not been digitised. Reading the file itself means Kew, or a published transcript.
Frequently asked questions
Who wrote the Action This Day letter to Churchill?
Four Bletchley Park codebreakers signed it, in this order at the foot of the page: A M Turing, W G Welchman, C H O'D Alexander and P S Milner-Barry. The letter is headed "Hut 6 and Hut 8" and marked "Secret and Confidential / Prime Minister only". The National Archives glosses those two huts as the sections handling Army and Air Force Enigma and Naval Enigma, though the letter's own section headings say "Military and Air Force Enigma" for the first of them. Milner-Barry was the one who physically carried it to 10 Downing Street.
What did the Bletchley Park codebreakers ask Churchill for?
Three things, all of them small. About twenty more untrained Grade III women clerks, so that a machine room that had stopped working nights could restart them. About twenty trained typists, so that intercepted Middle East wireless traffic could actually be decoded, a backlog the letter dates to May. And a detachment of the Women's Royal Naval Service to take over testing machine output, which had been promised in July and, in the letter's words, "nothing has been done" about by late October.
What was the "Action This Day" sticker?
A red printed label attached to minutes Churchill wanted dealt with immediately, rather than a phrase he wrote out by hand. The National Archives describes the note of 22 October 1941 as a handwritten minute to General Ismay "bearing a red 'Action This Day' sticker". The label is why this particular exchange is remembered by that name, and it did real work here: Ismay's reply opens by describing how he acted "on the receipt of your minute at Flag 'A'", and lists the Ministry of Labour and the Admiralty as the offices he went to.
Did the codebreakers get into trouble for going over their management's heads?
There was friction, though nobody appears to have been punished for it. Milner-Barry recalled meeting Commander Denniston in a corridor days later and receiving "some rather wry remark about our unorthodox behaviour", adding that Denniston "was much too nice a man to bear malice". The National Archives records a sharper aftertaste: the initiative "caused tensions at Bletchley Park and the signatories were dubbed the 'wicked uncles'."
Can you read the letter at The National Archives?
Yes, at Kew. The file is HW 1/155, its covering date is 21 October 1941, and its status in the catalogue is open. It has not been digitised, so there is no full scan to read from the catalogue entry, though The National Archives publishes images and a partial transcript of the letter, of Churchill's minute and of Ismay's reply on its own story page about the file. The complete text is available through published transcripts, including the collected Turing writings.
Everything in this story travelled by radio before anyone could argue about who would type it up, and hand-sent radio in 1941 meant one alphabet above all others. If you want to try that end of the chain, the Morse code translator will encode and decode it a letter at a time. And if you would rather start where a codebreaker starts, with a message and no idea what made it, the cipher identifier will take a first guess at the method.
Sources
- The National Archives, Discovery catalogue, HW 1/155, "Request for more staff sent to PM, response and action taken Nov 18", covering date 1941 Oct 21, catalogue status open, not digitised (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C4463383
- The National Archives, "A dramatic plea for Churchill's help from Bletchley Park" - images and partial transcripts of the letter, of Churchill's minute of 22 October 1941 and of Ismay's reply of 18 November 1941; also the September 1941 visit, Travis's role and the "wicked uncles" nickname (retrieved 10 August 2026): https://www.nationalarchives.gov.uk/explore-the-collection/stories/a-dramatic-plea-for-churchills-help/
- A M Turing, W G Welchman, C H O'D Alexander and P S Milner-Barry, letter to the Prime Minister, 21 October 1941, printed in full with an introduction by B Jack Copeland as chapter 7 of The Essential Turing (Oxford University Press, 2004), pages 336-340; Copeland's introduction quotes P S Milner-Barry, "'Action This Day': The Letter from Bletchley Park Cryptanalysts to the Prime Minister, 21 October 1941", Intelligence and National Security 1 (1986), pages 272-273 (retrieved 10 August 2026): https://webhomes.maths.ed.ac.uk/~v1ranick/turingletter.pdf
- The National Archives, Discovery catalogue, series HW 1, "Government Code and Cypher School: Signals Intelligence Passed to the Prime Minister, Messages and Correspondence" - scope and content note, source of the BONIFACE code name and of the statement that each file holds the documents passed on "complete with annotations and minuting" (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C9280
- The National Archives, Discovery catalogue, HW 14/19, September 1941 - directorate paper on staff problems, recruiting and pay; Hut 6 problems presented by G Welchman; WRNS complement of Hut 11 totalling 220 (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C5317536
- The National Archives, Discovery catalogue, HW 14/31, 11 to 20 March 1942 - "Detailed paper by WG Welchman, Head of Hut 6, on Bombes and E priorities", the source for Welchman's role title (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C5317548
- The National Archives, Discovery catalogue, HW 14/26, 1 to 15 January 1942 - staff strength for December 1941; Gayhurst, Crawley Grange, The Camp at Steeple Claydon and Walton Hall requisitioned for WRNS accommodation; case for expansion of the signals intelligence organisation implemented by the Chiefs of Staff Committee (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C5317543
- The National Archives, Discovery catalogue, HW 64/43, 1 June 1942 to 30 September 1943 - "involvement of the British Tabulating Machine Company Ltd (BTM) with GC&CS. BTM produced Bombes and Hollerith tabulating equipment for GC&CS", the source for the firm's full name and for its supply of both machine types (retrieved 10 August 2026): https://discovery.nationalarchives.gov.uk/details/r/C11204141
