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Contributed by 
Dundee Central Library
People in story: 
Kennedy McConnell
Location of story: 
Eastcote, Middlesex
Background to story: 
Royal Air Force
Article ID: 
Contributed on: 
10 November 2005

Ken McConnell, veteran of Enigma, in 2005

(Kennedy McConnell was an R.A.F. electrical engineer working on the Turing designed "Bombe" decoding machines. In 2003 he produced a professionally filmed lecture series, which has been copied on to videotape and DVD. The full series, comprising approximately seven hours of detailed historical analysis, can be viewed at Dundee Central Library. There are additional copies of the film at the Bletchley Park Trust, the Scottish National Museum, the Imperial War Museum and the National War Museums of America, Australia, and Canada).

When Britain declared war on Germany in September 1939, I was studying electrical engineering, which was a Reserved Occupation. However, after the Dunkirk evacuation in June 1940, when a German invasion was imminent, I volunteered for the RAF. I was trained as an electrical technician, and posted to 143 Squadron, Coastal Command. For the next two years, I worked on Blenheims and Beaufighters and served on various UK stations. I was then selected to join a technical team which was being assembled for some top secret project. After passing a rigorous entrance exam, and signing the Official Secrets Act, I found that this team would be helping cryptographers to attack the German ENIGMA codes.

Throughout the Second World War, all German air, land and sea forces used Enigma machines to encipher their radio signals. At least 50,000 were in service by 1945. Because of its complex mechanism and variable circuitry, this portable electro-mechanical machine was able to change plain text into scrambled output and provide over 150 million permutations. Consequently, Hitler and his intelligence advisers were convinced that their radio traffic would be completely secure. This proved to be a disastrous assumption, because the combined skills of cryptographers and engineers enabled us to break the Enigma codes on a daily basis from 1940 to 1945. The resultant intelligence was code named ULTRA.

The secret of this historic success was an amazing machine invented by Alan Turing, who was a famous mathematician. His brainchild was the forerunner of the modern computer. Thousands of Enigma signals were intercepted daily at receiving stations located throughout Britain. All these intercepts were relayed by teleprinter to the code breaking headquarters at Bletchley Park. From this hour-by-hour supply of raw material, our cryptographers applied their mathematical expertise to deduce programmes for the Turing machines.

All possible Enigma permutations were then tested at a rate of 1,000 per minute. This procedure continued until the correct settings were identified. This search could last from a few hours for the Luftwaffe, up to several days for the U-Boats. The cryptographers were then able to decipher all messages transmitted from that radio network. By 1943, these local networks were spread across Europe, Russia and North Africa. Consequently, we had to contend with many different codes. The settings on all Enigma machines were changed at one minute after midnight, so the same sequence of testing had to be repeated daily. The machines were operated 24 hours per day and 7 days per week by teams of WRENS. Two per machine were required on each shift, so about 1,700 were involved.

From 1940 to 1945, these unique machines were continually being improved in the light of operational experience. Later models were nick-named ‘Jumbos’. My role was to help with their development and maintenance. A total of 250 RAF Sergeants

were involved in this demanding duty. We had to work shifts like the Wrens. Minor faults were prevalent and had to be rectified urgently.

After VE Day in May 1945, Churchill ordered that all the Turing machines had to be dismantled. I was involved in this depressing task, before being demobbed in 1946.
For more than 30 years, we were forbidden to reveal that the Enigma codes had been broken. In 1978, the Government issued rather confusing guidelines on disclosure. We could tell what we had done, but not how we did it. Although my contribution was minor, I am proud to have been involved in this historic achievement, which influenced Allied strategy, saved thousands of lives, and helped to win the war.

Kennedy McConnell via Dundee Central Library
see also "An Amazing Wartime Secret" by the same author.

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Message 1 - MY SECRET WAR

Posted on: 11 November 2005 by Peter - WW2 Site Helper

Dear Mr McConnell

I found your story to be very interesting. Given that you were at Bletchley, it amply demonstrates how the work was kept secret and that only a very limited number of operatives knew the full picture. First some indisputable facts. You say that "After VE Day in May 1945, Churchill ordered that all the Turing machines had to be dismantled" Firstly, Churchill had left government by then and all decisions regarding Bletchley were made by the Labour government. Secondly, it is quite impossible to dismantle a Turing Machine; Turing machines are not physical objects but mathematical ones. They are not intended actually to be engineered (there being no point in doing so).

Alan Turing was a brilliant young theoretical mathematician, but his international fame as a mathematician came in 1950 with his ground-braking paper "Computing Machinery and Intelligence". Known at Bletchley as 'the Prof', Turing was but one of a remarkable team of cryptanalysts; more importantly you do not mention that the credit for the initial breakthrough of Enigma is shared by Turing and and Gordon Welchman. Nor do you mention the other great cryptographers, for example Joan Murray.

Turing was the genius who designed the 'bombe', but this was not as you say "the forerunner of the modern computer". A bombe was not in any sense a computer, it was a bank of thirty-six high-speed electrically driven Enigmas used to break daily Enigma keys being the essential basis for the solution of the 'Heer' and 'Luftwaffe' Enigmas.

You also say in "Amazing Wartime Secret - Part 4" (A6842676) that "Ultra identified all enemy infantry and panzer divisions stationed in Western Europe prior to the invasion". This was not the case, Ultra had a minimal role in identifying German units present in France or anywhere else. I should explain that during WW2 the Germans used two highly efficient encrypting systems, the first was Enigma, the second was what Bletchley termed 'Fish'. Fish came in various forms, the main two were 'Schlüsselzusatz' ('cypher-attachment' dubbed 'Tunny') and the 'Geheimschreiber' ('secret-writer' - dubbed 'Sturgeon'). These machines were arguably more secure than Enigma, but much bulkier and thus not suitable for either submarines or the air force, nor were they issued to the army in the field. The big advantage of the Enigma machines was that they were portable and could be carried in a small vehicle.

Ultra had great success against the navy and air force Enigmas, but not against the German army Enigma. The reason for this lies with the signalling practice of all armies in that units mainly use land lines and dispatch riders; army radios, in the main, are of limited range and mainly used between tanks and by artillery observation posts. At regimental and divisional level and up to army level, where radio use was unavoidable, Enigma was used, but in all radio communications with Berlin and for all high-grade secrets, Fish was used. Fish and Enigma had little in common and the design of Tunny (the 'Schlüsselzusatz') differed completely from that of Enigma. The messages also differed in format, Tunny was a high-grade very fast teleprinter and its messages often contained thousands of letters, whereas an Enigma message seldom exceeded a few hundred.

Fish used the Lorenz Cypher code. It was Colossus (the true forerunner of all computers, and the world's first large-scale electronic digital computer) that broke the Lorenz codes. It was Fish and Colossus that were of paramount assistance in the Normandy Landings rather than Ultra. Colossus was designed by Tommy Flowers, not Alan Turing. Also it was John Tiltman and Bill Tutte who cracked the Lorenz code, not Turing. Knowledge of German dispositions in France in the run-up to D-Day also came from breaking the Japanese military attaché's coded report back to Tokyo on German plans to counter an invasion. Shaun Wylie, who was at Bletchley Park from 1941 to 1945 says that "The breaking of the Enigma machine cyphers is invariably cited as the great achievement of the Bletchley Park codebreakers. But the breaking of the German enciphered teleprinter traffic, given the generic codename of 'Fish', was a far greater achievement". Colossus gave access to all German top secrets including all messages from Hitler to his front-line generals. By D-Day the Allies had the entire German Order of Battle, in detail, right down to regimental level. And as early as April 1943 the first link on the Russian front had been broken, that between Berlin and Army Group South, and the earliest decrypts gave full details of plans for the German counter-offensive at Kursk.

You also underestimate the speed of the Colossus, not 1,000 calculations per minute, but 5,000 per second - i.e., 300,000 per second. Greater speeds could have been achieved but at higher speeds the paper tape broke. It also seems to me to be the you were dismantling in 1946. I am sure that you will find Tony Sale's website of great interest: links

In "Code Breakers" edited by F.H. Hinsley and Alan Stripp:
"An Introduction to Fish" by F.H. Hinsley
"Enigma and Fish" by Jack Good
"Hut 8 and Naval Enigma" by Joan Murray.

In "Action This Day" edited by Michael Smith and Ralph Erskine:
"Breaking Tunny and the Birth of Colossus" by Shaun Wylie.
"Colossus and the Dawning of the Computer Age" by Jack Copeland.
"Bletchley Park, Double-Cross and D-Day" by Michael Smith.

"Battle of Wits" by Stephen Budiansky.

Peter Ghiringhelli


Message 2 - MY SECRET WAR

Posted on: 11 November 2005 by Peter - WW2 Site Helper

Sorry for the typos.

"You also underestimate the speed of the Colossus, not 1,000 calculations per minute, but 5,000 per second - i.e., 300,000 per second."

should read:

"You also underestimate the speed of Colossus, not 1,000 calculations per minute, but 5,000 per second - i.e., 300,000 per minute".


Message 3 - MY SECRET WAR

Posted on: 11 November 2005 by Peter - WW2 Site Helper

Tony Sale has created an excellent online simulation of both Enigma and Lorenz here links and you can try your skills at decrypting a message. There is also an interactive full description of Bletchley Park.


In the penultimate sentence of my post I said "It also seems to me to be the you were dismantling in 1946".

this should be:

"[Colossus] also seems to me to be the machine you were dismantling in 1946}.


Message 4 - MY SECRET WAR

Posted on: 28 November 2005 by Dundee Central Library

Dear Peter

Thank you for your detailed contribution, which I will forward to Mr. McConnell.


David Kett (Dundee Central Library)


Message 5 - MY SECRET WAR

Posted on: 01 December 2005 by Dundee Central Library

Thank you for your comments on the above article. This entry was
restricted to less the two A4 pages. I have compiled much more comprehensive accounts
of my wartime involvment with the Turing Bombes. However, here is my
response to some of your statements.

(1) We started dismantling the Bombes on May 9th 1945. Churchill remained
as Prime Minister until he resigned on May 23rd. Parliament was dissolved
on June 15th. The General Election which was held July 5th. The resultant
victory for the Labour party meant that Attlee became Prime Minister.
Churchill invited him to the Potsdam Conference on June 15th.

(2) I am aware of Gordon Welchman's contribution. Mainly the invention of
the Diagonal Board. His book 'The Hut Six Story' is a useful reference
source. It is evident that he is a brilliant mathematician. He also gives much
overdue credit to Harold Keen, of B.T.M., who turned Turing's theoretical
concept into engineering reality. Did you know that a team of volunteers has
been trying for several years to rebuild a Bombe. I have been helping both
financially and technically. The man in charge is of the Bombe Rebuild
Project is John Harper. The relevant website is :

(3) Regarding the searching speed of the Bombes. I have witnessed hundreds
of 'runs'. This was the term we used for the testing of one set of Enigma
rotors. As you will be aware, the German Air and Army machines had five rotors
available. The Navy and U-boats had eight. The daily Key selected three
rotors. It also stated which Stekkers were to be cross plugged. The operator
then chose six letters at random before synchronising with the other Enigmas
on his net. With most intercepts , our cryptographers had no idea which
three rotors would be in use on any given day. Consequently, each Bombe had to
start testing every Menu on each of the 60 or 360 options available to the
German programmers. The maximum possible permutation from any one set of
three rotors is 26 x 26 x 26 =17576. We had to keep daily records of
efficiency. Our target was 98%. Downtime had to be minimised. We were told that
every hour lost could mean that a U-Boat Pack was 20 miles closer to a
convoy. Theoretically, the high speed versions of the Bombe could complete a run
in 17 minutes. Hence my statement of 1,000 tests per minute.

(4) I was not involved with Colossus, although I have read about Tommy
Flowers 'Heath Robinson'. Also Tony Sale's rebuild project. It is worth noting
that the later version of Bombes used thyratron gas-filled relays in place of
Siemens high speed relays. This experience proved that valves would not
fail if they were kept alive.

I was 85 last week and my health is failing. This was the motivation for
recording my experiences on video. Although I do realise that there are flaws
in my version of events, it will stand as a unique record for posterity.

Kind regards,



Message 6 - MY SECRET WAR

Posted on: 03 December 2005 by Peter - WW2 Site Helper

Dear Kennedy

Many thanks for that further very interesting information. I am sure that many others will enjoy reading it too. If you can find the time please do post more.

My very best wishes to you and warmest regards,



Message 7 - MY SECRET WAR

Posted on: 21 December 2005 by Dundee Central Library

Sorry for delay in responding to some of your other comments.

(1) I am a great admirer of the Colossus. My regret is that I was not
involved. Although I did not meet Tommy Flowers, I worked with his colleagues
from Dollis Hill, who were devedoping and maintaining the COBRA machines. You
probably know that these did the same job as the Turing Bombes. I have
defended Colossus against the American claim that the ENTAC was the first
operational computer. Colossus predated Entac by exactly two years.

Please remember that for four years before Colossus became operational,
Ultra had influenced Allied strategic decisions and saved many thousands of
The most important contribution was arguably during the Battle of the
Atlantic. The value of Ultra was clearly demostrated when Doenitz added a fourth
rotor to the U-Boat Enigmas. During the following ten months 'blackout', when
BP could not break the Shark key, Allied merchant shipping losses reached
crisis level. Britain was being starved of essential war material. The
situation was transformed by the restoration of Ultra.

(2) I disagree with your statement that we did not decipher many German
Army Enigma keys. Where land lines were not available, the number of radio
networks multiplied as the war spread across Europe and Into North Africa.
Consequently, Enigma keys were opened and closed accordingly. For example,
YELLOW was used only during the Norwegian campaign. To the best of my
knowledge, the Lorenz was not used in field operations. The defeat of the Afrika
Korps was hastened by the deciphering of Rommel's ENIGMA messages to
Kesselring. According to my records, Wehrmacht keys were penetrated as follows:
1940/41 = 6, 1942/43 = 23, 1944/45 = 30.

Kind regards from Kennedy McConnell


Message 8 - MY SECRET WAR

Posted on: 25 January 2006 by Peter - WW2 Site Helper

Dear Kennedy

I have now reread your original post and not that you have edited it and have removed all reference to 'bombes' and to 'Turing machines'. In your original version you spoke throughout of the bombe saying that it was "the forerunner of the modern computer". You have now altered this to "The secret of this historic success was an amazing machine invented by Alan Turing, who was a famous mathematician. His brainchild was the forerunner of the modern computer".

It was this that prompted me to reply and point out that a bombe was not in any sense a computer, it was a bank of thirty-six high-speed electrically driven Enigmas used to break daily Enigma keys being the essential basis for the solution of the 'Heer' and 'Luftwaffe' Enigmas. However you still refer to the "Turing machine". As I pointed out, a Turing machine is a mathematical concept not a real entity. It is a mathematical concept, a theoretical model of computation that uses an underlying finite-state automaton with an infinite tape to use as memory. All computers, advanced main-frame down to home PCs, are faint imitations of Turing machines in that they have finite amounts of memory. They are as near as we can get to a Turing machine in the real world.

As I pointed out, the first ever computer was the Colossus designed and built by Tommy Flowers. I referred to the searching speed of the Colossus, not of a bombe. I have a web page here links which you may find of interest.

Of the Enigma machine, you say in Part 1 (A6840984) that "The keyboard had the alphabet arranged in three rows ..." and indeed nearly all the illustrations of Enigma show this, but as Alan Stripp points out "The model with an A-Z keyboard shown in several books on Enigma, is a Polish-French replica, not an actual Enigma machine'. The German Enigma had 26 letters arranged in the offset pattern of a normal German typewriter, the first line being QWERTZUIO, it was not alphabetically arranged in 3 rows.

You say that "Five differently wired rotors were provided for each Army and Air Force Enigma, and eight for the Naval version". All accounts, drawings, and photographs I have examined show Enigma to have three rotors (with a fourth rotor added later for the naval Enigma), none with five or eight. There were five rotors to select from, but only three were fitted. You say that "The combination of five interchangeable rotors and ten pairs of stekkers enabled the Enigma machine to produce approximately 150,000,000,000,000 encoding positions". But that figure, 150 million million, was for the total number of stecker pairings; the total number of possible daily keys was consequently far higher: about 159 million million million, according to Alan Stripp.

Regarding the British bombe (incidentally, Turing's device was called a 'bombe' simply because it bore a passing resemblence to Rejewski's bombe), you say "A detailed technical description of the design and construction of the Turing bombe is outwith the scope of this article". But asside from the complexity of wiring, a Bombe was a mechanical device, essentially a series of Enigma machines linked together. It was only the prototype that arrived at Bletchley, christened Victory, on 14 March 1940 - but this was a disappointment. The design was modified and the new bombes, christened Agnus Dei or Agnes for resemblanceshort, arrived onaside 8 August.

In Part 2 (A6841208) you say that "Ultra revealed from 29th July that a large invasion fleet of barges, tugs and motor boats was being assembled in French and Belgian harbours". I think you underestimate the part played by the RAF and aerial photography in this. Further, regarding the North African campaign, you say that "Ultra kept Montgomery informed of Rommel’s plight but he still failed to trap him. Churchill was incensed by this lack of initiative which prolonged the war in Africa by several months". On what grounds do you say this? I think you may be confusing this with Churchill's telegram to Alexander (ref CS/1689, IZ 2128 - 8 Nov '42 Churchill papers, 20/82) "It is most necessary that the attack be resumed before 'Torch'" but this telegram was sent before Churchill had received any description of the previous day's battle, as soon as he realised that Alexander was merely pausing for an instant he sent him a telegram of encouragement. Churchill, of course, did not communicate directly with Montgomery but with his superior, Alexander.

In Part 4 (A6842676) you still claim that "Ultra identified all enemy infantry and Panzer divisions stationed in Western Europe prior to the invasion". This wasn't the case, there are many sources confirming this. To give but one, Carlo D'Este observes in "Decision in Normandy", at page 122 "As a general rule the information disclosed by ULTRA during this time was low-level and fragmentary". 'Ultra', by the way,"is the term used to describe the fruits of breaking any enemy high-grade machine cypher" (Ibid, page 122)

Regarding the capture of the Ludendorff Bridge at Remagen and the subsequent attempts of the Germans to destroy it, you say that they attacked with "heavy artillery, naval frogmen and V2 rockets ...". V2 rockets were never used for this purpose and would have been impossible to aim at such a small target. The bridge collapsed under attacks by the Luftwaffe, artillery, floating mines, and swimmers with demolition charges. But it was all too late and by the 24th eight newly constructed bridges were in use.

You also say that "By January 1945, Stalin’s armies had driven the German forces out of Russia." This is misleading, they were driven out of Russia well before that, and out of the USSR by mid 1944; by August 1944 Soviet forces were on the border of East Prussia. By January the Eastern Front was well into Germany.

Kind Regards

Peter Ghiringhelli

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