Women Codebreakers; the hidden female heroes of code cracking

Without doubt, if you ask someone to name some WW2 codebreakers, all the names they are likely to come up with will be those of men. Alan Turing, Gordon Welchman, Alistair Denniston, Dillwyn Knox, John Tiltman, Hugh Alexander, Stuart Milner-Barry, and Bill Tutte are names which might figure in a brief list of leading British codebreakers. In the USA, the list might include William Friedman, Joe Desch, Elvin Urquhart, and Frank Rowlett.

This could suggest that codebreaking is an exclusively male field, one to which women were unfitted to contribute. But nothing could be further from the truth; the reason women rarely participated at the higher levels of codebreaking was largely the result of male prejudice, not of female inability.

Even well before WW2, a several talented and determined women showed great codebreaking skills. Elizebeth Friedman (1892-1980, wife of William), started work as a codebreaker for the US War Department in 1919 and later worked for the US Navy, scoring notable successes against smugglers attempting to bring alcohol and other contraband into the USA in the prohibition years.

Elizebeth Friedman – US codebreaker

In the UK, Emily Anderson (1891-1962) was a ‘Hushwaac’ in WW1 – one of twelve women from the WAAC who were recruited as codebreakers in 1917 – and she stayed on after the war in GCCS as its sole female codebreaker. She has been described by John Ferris as ‘among the best cryptanalysts in the world’.

At Bletchley Park, there were eventually some 9,000 people employed, contributing to the work of this mighty production line of intelligence; intelligence derived from breaking enciphered enemy radio messages.

Women outnumbered men at Bletchley Park by about 3 to 1

In one sense all were ‘codebreakers’; they were, after all, employed in an institution dedicated to breaking enemy codes (and ciphers). However, the vast majority weren’t actually wrestling mentally with the problems of working out what GPCFF WNBFT IYRAM BBXFE TEQCB OHJJR could possibly mean.

The pyramid was a very flat one, with few at the top, challenged daily to interpret apparently meaningless strings of letters. Below them, in the broad lower reaches, were hundreds involved in the essential work of sorting, transcribing, indexing, translating and typing. The majority of these ancillary staff were women – by 1945, women at Bletchley outnumbered their male colleagues by three to one. One of them, Betty Webb, was doing such valuable work that she was transferred to the Pentagon between VE Day and the surrender of Japan in August 1945.

Although the women were, by and large, officially recruited for these more lowly roles, perceptive senior men deliberately sought out or recruited talented women who had codebreaking potential.

Renowned among these was Dilwyn (‘Dilly’) Knox, who studied the interview notes made by the Foreign Office interviewer, and then drafted some of the brightest women into his team. All of his immediate team were women, giving rise to the nickname ‘Dilly’s Fillies’, supposedly picked for their good looks, but it was actually their brains which caught Dilly’s attention.

Amongst these hand-picked girls were Mavis Lever, Margaret Rock, Claire Harding, and Phyllida Cross, and their success against Italian Naval Enigma gave Admiral Cunningham the opportunity to surprise the Italian Mediterranean Fleet at Matapan, and inflict such damage that it was never a serious threat again. Admiral Godfrey, Director of Naval Intelligence, credited Knox’s team with this victory, and Cunningham himself made a point of visiting Bletchley to thank the team in person.

So, there were women codebreakers at Bletchley – but they faced an administrative hurdle: Civil Service rules defined certain jobs as male-only, making it impossible for a talented woman to be officially classified (and paid) as a codebreaker.

Obtaining appropriate promotion and pay for codebreaking women meant that, initially at least, they had to be given some other job description. Joan Clarke, for example, was recruited into codebreaking by Gordon Welchman because of her proven mathematical ability, but had to apply to be a ‘linguist’, despite admitting on her application form that she had no linguistic skills.

Joan Clarke, talented mathematician and codebreaker, could
only be officially classified as a ‘linguist’

In the USA, no such subterfuge was required. Even before Pearl Harbour, the US Navy started to recruit women from prestigious colleges to be trained as cryptanalysts. The US Army followed suit, and by the end of the war, about 11,000 women were codebreakers, outnumbering their male colleagues.

In the UK, therefore, male prejudice worked in two ways: firstly, senior (male) staff were frequently of the opinion that women weren’t good enough for codebreaking work, and secondly, even if a woman was deliberately recruited (by a more perceptive man) as a codebreaker, she could not be officially classified as one.

The inevitable result is that anyone now scanning contemporary staff registers, pay lists, etc, will underestimate the number of women codebreakers, because their skills and roles have been buried under inappropriate job descriptions.

We will never know how many of the six or seven thousand women at Bletchley were actually codebreakers, despite being listed as typists, filing clerks, indexers or secretaries. We can, however, be sure that many of them were codebreakers, and their skills and dedication contributed to Allied victory.

‘National Geographic’ pays tribute to Betty Webb,
who worked on Japanese messages at Bletchley Park, and later in the Pentagon

Finding Enigma: from fields to flea markets – strange places Enigma machines have been found

Because, occasionally, previously unknown Enigma machines come to light (especially in Eastern Europe) our knowledge about how many Enigma machines survive, and how many were made, improves with time.

The number of known survivors increases, and will doubtless continue to increase, but one fact stands unchanged: the vast majority of all Enigma machines made (perhaps 45,000) have perished – destroyed in battle, sunk at sea, or deliberately smashed beyond repair to keep their secrets from the enemy. A mere one machine in a hundred has survived, and a good proportion of these are safely held in museums all over the world.

However, the wartime distribution of Enigma machines was virtually world-wide, and the final stages of the war so disorderly, that there could be no systematic gathering in of all the machines at that point.

They were abandoned, stolen or lost in a hundred and one places scattered over a hundred thousand and one square miles. The result is that no-one knows where the next Enigma machine may be found.

Enigma Machine Found in Flea Market

Thirty years ago, when I first became interested in Enigma machines, and they began to appear in auctions for a few thousand pounds, I encountered an urban myth – one of those things that happen to ‘a friend of a friend’.

This particular myth told of a man who had seen in a market somewhere a ‘funny sort of typewriter’ for sale for a few pounds. He didn’t buy it, of course, but when he belatedly discovered what it actually was, he rushed back – to find it had gone.

I have before me now a 30-year old newspaper article about a man who collected (and used) spy radios, which ends with:

‘His greatest regret is failing to spot a German Enigma machine for £5 in (London’s) Brick Lane market. He mistook it for a calculator.’

Mind you, such markets can yield prizes. A few years ago, a maths professor in Romania spotted a ‘funny looking typewriter’ in a flea market, priced at 100 Euros. Recognizing exactly what it was, a 3-rotor Enigma machine, he snapped it up, and then sent it to auction, where it fetched 45,000 Euros. That was by no means the end – it was next recorded on sale in New Orleans for $245,000.

I thought my luck was in when I spotted, in 1998, amongst a long list of electronic equipment advertised for sale in a wireless magazine, a ‘German Enigma Coder’. The entry itself was minute – about 15mm x 4mm – so I felt that I’d stumbled across an unrecognized treasure.

A quick phone call soon dispelled any such hopes – it wasn’t a German Enigma machine at all; it was a (perfectly respectable) post-war Swiss NEMA cipher machine.

Perhaps the last place you might expect to find an Enigma machine is in the exact spot where it last saw service, but that’s what happened in the Channel Islands, the last territory occupied by the Nazis to surrender.

The surrender documents were signed on 9 May 1945, one day after the official surrender on Europe’s mainland. The German soldiers were then allowed to leave the islands (on Royal Navy vessels) without let or hindrance, but were not allowed to take with them any military equipment.

Thus the Enigma machines which had been in use in the most heavily garrisoned part of Europe stayed behind, so when nowadays you see an Enigma machine in Jersey or Guernsey, it’s in exactly the place where it served during the war.

26 Enigma Machines found in Spanish Military Store

Surprisingly, it was not until 2008 that a group of really early Enigmas was found in a locked military store in Spain, overlooked and neglected for years. 26 Type D Enigmas, supplied to Franco in 1936 to bolster the Nationalist cause during the Spanish Civil War, were taken out of service in the 1950s, and had lain undisturbed for the next fifty years.

A number have since been presented to museums in Spain and elsewhere, including Bletchley Park and GCHQ.

Spanish stamp marking the stash of Enigma machines discovered

Battlefields Yield Enigma Remains

Metal detectorists are these days searching not only battlefields, but also locations where temporary camps, offices and staging posts were set up. The result is a rich haul – not so much of Enigma machines, but of the recognizable remains of Enigma machines.

Occasionally, a whole body of a machine will be found, but it’s often only a few handfuls of metal fragments, possibly including a rotor or two which may still carry the unique serial number of the machine of which it was part. Such fragments are undoubtedly of interest, but well beyond the possibility of restoration into a working machine.

Even in a decayed state like this, Enigma machines are still sought after.
This one is currently for sale by The Enigma Museum.

Underwater Enigma: MachineS found on Sea Bed

When the sunken U-Boat U534 was raised off the Danish coast in 1993, two Enigmas were found on board, somewhat corroded by 48 years lying in salt water, and these can now be seen in the Visitor Centre in Birkenhead, England.

U534 which was raised from the Danish seabed contained two Enigma Machines.
The picture above shows the rebuilt conning tower (and the new paint!)
The Enigma machines salvaged from U534

Rather different circumstances surrounded the discovery of an Enigma in the Bay of Gelting in the Baltic Sea in December 2020. An environmental group, scouring the sea bed to locate and remove old cables and nets, spotted a complete Enigma machine, and managed to raise it to the surface. A local museum has promised restoration, a considerable task, given 75 years of saltwater corrosion.

The Enigma machine found on the Baltic Seabed by an environmental clean-up group.
Image by Cristian Howe

6 more Enigmas found on Baltic seafloor

The Baltic sea seems to be somewhat of an Enigma machine graveyard. While searching for a lost propeller, a salvage diver located 6 more Enigma machines near Schleimunde. The find was originally made at the beginning of 2021, but due to the heavily encrusted state of the machines, they were not identified immediately for what they were.

Some had obviously been mutilated before disposal. Presumably the dumping of these machines is associated with the scuttling of nearly 50 U-Boats in this area on the night of 4/5 May 1945. My guess is that more divers will be out deliberately hunting for more Enigmas later this year, and they will find more of them!

Salvage diver – Christian Hüttner – poses with Enigma machines he discovered in the Baltic.
Image: Christian Hüttner Salvage Divers

So, no-one knows where the next ‘new’ Enigma machine will appear, or who will find it. We can be certain that there are more to be found, so keep your eyes open, and it may be you!

If you’d like to get ‘virtually hands-on’ with an Enigma machine – book a Dr Enigma online presentation and demo and see for your own eyes this fascinating machine and story.

Dr Enigma visits HAM Radio Fair in Germany

There were so many thousands of valves, condensers, tuners, aerials, coils, antennae, and numerous boxes of electronic gear embellished with dials, knobs and switches, that it was easy to accept that the recent Amateur Radio Fair in Friedrichshafen was Europe’s largest.


For some years now, that has been the proud boast of this southern German city, which will be better known to many as the home of the Zeppelin works, 90 years ago the world leader in airship design and operation.


The support from radio hams was world-wide – there were (amongst others) stands from Spain, Qatar, Brazil, Italy, Portugal, Israel, and Turkey – and many of these radio hams were able to experience hands-on Enigma operation at the Fair.

Without radio, there would have been no need for the Enigma machine, so it is not surprising to discover that one section of the huge fair comprised eight stands devoted to Enigma and other crypto devices.


Pioneered by Tom Perera from the USA, there has been a strong Enigma presence at the Friedrichshafen Fair for some years, and this has become an important international focus for those interested in crypto.

Exhibiting and selling on the eight stands were enthusiasts from USA, Germany, UK, The Netherlands, and Switzerland, and Dr Enigma was right in there with them. The Pereras (father Tom and son Dan) and Klaus Kopacz both had Enigma machines on display.


Perhaps the greatest excitement came during the setting-up day when two Enigma machines were brought in for sale, and were quickly snapped up by eager buyers – and buyers who needed to be well organized enough to be able to produce tens of thousands of Euros in cash to close the deals.

On the first full day of the Fair, one of the conference rooms was the venue of an Enigma Forum, in which several papers were delivered reporting on new developments and discoveries in the Enigma world.


Amongst these was a detailed account of the restoration of an Enigma which had been found in a wood shed in Belgium, an explanation of the latest analysis of the evolution of the steckerboard, and a report on progress being made in the decryption of several hundred original Enigma messages recently discovered in an archive in Berlin.

Tom Perera, organizer of the Forum, has now invited Dr Enigma to present a paper at Friedrichshafen fair in 2020, surveying the work done at Bletchley Park during WW2.

Putting this work in context will provide a useful contrast to the intense scrutiny of the machine itself.

To book Dr Enigma for a fascinating talk and hands-on demo with an original Enigma machine – contact us, or visit the Enigma events page.


Alan Turing – Great British Icon

In early February, BBC 2 screened the final instalment in their series ‘Icons: The Greatest Person of the 20th Century’. In previous instalments, viewers had been asked to vote for the greatest within seven different categories: arts, sport, politics, science, etc. In the final show, the winners in each category were pitted against each other, giving viewers the challenge of judging, say, Ernest Shackleton against David Bowie and Alan Turing.

Inside Facebook HQ: a giant rendition of Alan Turing made from dominoes

In the event, Alan Turing won (or perhaps I should say that Chris Packham, who made the case for Turing, won). However, a real confusion arises from the inclusion in the series’ title of two distinct ideas: ‘greatness’ and ‘icon’. To assess greatness, we need an expert to recount the achievements of a particular man or woman, and explain why these are outstanding or groundbreaking, and thus worthy of the title ‘great’.

Being an icon does not require demonstrable greatness; it must rest upon a person’s having been widely enough known, and inspirational enough, to excite widespread admiration. It is hard to see how Shackleton, admirable though his achievements undoubtedly were, could possibly now be regarded as an icon – he just isn’t well enough known.

Turing scores well as both great and iconic. His achievements can be said to rest upon a few overly simple labels: ‘Codebreaker’, ‘Helped to win World War 2’, and ‘Father of the Computer’. Imperfectly understood by most, these labels are enough to convince us of his greatness. In addition, his determination to overcome personal difficulties and challenges, culminating in disgrace and criminal conviction, are truly inspirational and the last fifteen years or so have undoubtedly seen Turing develop the aura of an icon. An apology by the Prime Minister in 2009, worldwide celebrations in 2012 to mark the centenary of his birth, and a Royal Pardon in 2013, are all indicative of the evolution of his iconic status.

He won the contest – a fitting tribute to a clearly great man who continues to provide inspiration to many who do not fit easily into the slots society would force them into, but who battle on. A Great British Icon.

Did the Nazis know the British were breaking the Enigma codes?

I am often asked whether the Germans had any idea that the British were successfully breaking Enigma during the war.

Surely, they say, there were German spies in Britain who would have been able to pick up some clues, and to report their findings back to Germany? It often comes as a surprise to them when I tell them that, firstly, all the German spies in Britain were directly controlled by the British, and that, secondly, British achievements were not known of in Germany until the 1970s.

Masterman was the Chair of the ‘Twenty Committee’, and his 1972 book revealed how the whole German spy network in UK was controlled by the British.

It seems that the Enigma machine – or, rather, its ciphers – were seen in Germany as unbreakable. After all, there were theoretically 3 x 10114 possible cipher patterns which the basic three-rotor machine could create, and testing all these possibilities one after the other is beyond modern computing power even now, and so was well beyond anyone’s wildest dreams during WW2.

The three-rotor Enigma had 3 x 10114 possible cipher patterns. Pic: James Martin/CNET and

With this exaggerated belief in the inviolability of the Enigma system, its users never stopped to think – or even to test – whether it could really withstand an organised attack using mathematics rather than the ‘brute force’ approach of attempting to test all those possibilities in succession. (See: War Hackers: Why Breaking Enigma is Still Relevant to Cybersecurity Today).

There were occasions when Allied successes in combat were such that questions were raised on the German side – investigations were set up to identify what had gone wrong, had valuable information been leaked?

Inevitably, when all the possible explanations were examined, unfounded faith in Enigma steered the investigators away from realising that Enigma might actually have succumbed to a sustained mathematical attack.

With hindsight, we can now identify occasions when more rigorous analysis might have revealed to the Germans that Enigma was, at least, breakable, even if not broken. Such a conclusion might have prompted tightening up or changing the way in which Enigma was used, or perhaps changing the wiring patterns of the rotors. The latter never happened, and such changes as were made to the operating procedures were never sweeping enough to shut out Bletchley for long.

Of course, great care had to be taken over Allied use of Intelligence derived from breaking Enigma. Over-hasty or injudicious use of such Intelligence could well have suggested to the Germans that Enigma-encrypted messages were being read. No-one on the Allied side, therefore, was permitted to base any action on a decrypt, unless there was also another way in which the relevant Intelligence might have been acquired.

The care with which Enigma-derived Intelligence was handled prevented its source from being discovered, and this, together with Germany’s unjustified faith in the machine’s power, meant that knowledge of Allied breaking of Enigma remained a secret not just throughout the war, but until 1974, when The Ultra Secret, a book written by RAF Intelligence officer Frederick Winterbotham, revealed the truth.

Ultra Secret 1e Dw
Winterbotham’s book, published in 1974, was the first to reveal the scale and importance of Enigma-breaking at Bletchley Park.

Even so, there was a perilous moment when Schellenberg’s handbook for the planned invasion of Britain (produced in 1940) reported that MI6 had moved its Communication Section from Broadway to Bletchley Park, and that its duties included Wireless/Radio communications.

The implications of this accurate observation, correctly linking MI6, Bletchley, and wireless communications, were never followed up. The evidence lay upon the printed page – but was never spotted.

How many Enigma machines are there left?

How many Enigma machines are there left in the world? This is a question frequently asked at my Enigma presentations. It is impossible to answer this precisely, as nobody knows.

A 3-rotor Enigma machine

There is no obligation on the owner of an Enigma machine to register it in any way – it’s not, after all, a transmitter – but fortunately, the late David Hamer decided years ago to keep records of all the machines he heard about, both those owned privately, and those in museums and other public collections.

Obviously, such a list can’t be complete (I know of several Enigma machines which are not listed, and there are almost certainly many more) but it’s the nearest thing we have to a worldwide catalogue at present. As more Enigma machines are being discovered, and as it’s unlikely that a significant number of the machines listed have subsequently been destroyed, the list understates the number of survivors, rather than the reverse. Nevertheless, analysing the list produces some interesting results.

Numbers of known Enigma machines that still exist

  • 318 Enigma machines left TOTAL
  • 284 Enigma machines issued for use in or before WW2
  • 34 Enigma machines that played no part in WW2
  • 186 3-rotor Army/Air Force machines left
  • 63 4-rotor naval Enigma machines left

The most recently available version of the list shows 318 Enigma machines, of which 34 played no part in WW2, leaving 284 machines issued for use by Germany in or before the war.

These can be further subdivided into different types: for example 186 are standard 3-rotor Enigma machines of the sort used by the Germany Army and Air Force, and 63 are 4-rotor naval Enigma machines (adopted on 1 February 1942).

So the list enables us to answer the original question, by saying that, roundly, perhaps around 300 WW2 machines survive, of which about 1 in 5 is a 4-rotor naval machine.

Close-up of the scrambler unit of a 4-rotor machine, one of the rarer Enigma types

However, as well as identifying the type of each machine, the list also includes the serial numbers of each. Every Enigma machine carries an individual serial number, which is not only stamped into the metal base (inside, and only visible when the rotors are removed), but also engraved into the rotors (including the reflector rotor) and included in the data shown on a metal label mounted centrally in front of the keyboard.

The case itself may also carry a small metal or plastic number plate. The label in front of the keyboard may give additional information about which manufacturer made the machine and when. This data can be used to provide an estimate of how many machines were made, even though the serial numbers are not members of one continuous series of numbers.

Enigma x 2! Ralph Simpson of The Cypher History Museum (San Jose), with Dr Enigma – each with their personal Enigma machines

The numbers are prefaced by a single upper case letter (there are 6 of these), which can be correlated with the machine type or user. For example, all naval machine numbers, whatever the model, are prefaced by ‘M’, for ‘Kriegsmarine’. Examining the numbers, and making some realistic assumptions, suggests that about 37,000 machines might have been made, of which at least 284 (less than 1%) survive. As noted above, about one fifth of the survivors are 4-rotor naval machines.

These conclusions must necessarily be tentative, but in the absence of original German records, they are the best we can do. They also suggest that published (unsubstantiated) estimates that there were as few as 20,000, or as high as 120,000 machines, are wide of the mark.

Following David Hamer’s death last year, other experts have volunteered to maintain and update the list. I’ll revisit this subject if any amendments are necessary.

If you’d like to learn more about the fascinating Enigma machine story, and play with one of these iconic machines yourself, you can attend one of my Enigma machine events or book me for your own.

Enigma Machine visits Silicon Valley Tech Companies

In late February, I flew to California with my Enigma Machine to deliver presentations on ‘The Greatest Hack in History’ at the request of a number of major tech companies including FaceBook, PayPal and Dropbox.

I was also invited to speak at the major tech news network CNET, who then wrote an article about my visit (which you can read here: Enigma: Up close with a Nazi cipher machine) and also did a photo shoot.

Interest in the talk and Enigma Machine demo was extremely high and it was a pleasure to be able to speak infront of such enthusiastic audiences at such sucessful and interesting companies. Visit the Gallery to see some pictures of my Silicon Valley Tech Tour, and keep an eye on the events page if you want to come and play with a real Enigma machine.

The Stolen Enigma machine

Bletchley Park – war station for Britain’s codebreakers – is nearly 100 miles from where I live, so I don’t go there at the drop of a hat. However, I do go quite often, my first visit being over 20 years ago but, because of the distance, I try to combine calling in at Bletchley with some other mission. This often means that I have my Enigma machine with me because I’m en route for a speaking engagement. Do I leave the machine in my car while I call at the shop, visit an exhibition, or meet up with a contact? I do not! When I’m asked why I lug the machine with me, I respond with another question: where is the only place from which an Enigma machine has been stolen recently? Answer: Bletchley Park.


1 April 2000 was a Saturday, and Bletchley was open (it was only open two days per fortnight back in those days). That night, the national news programmes reported that a ‘unique code machine had been stolen from Bletchley Park’. I found this both worrying and puzzling, because I didn’t think that the Bletchley Park Trust owned a unique Enigma machine. The basic facts soon surfaced: what had been stolen, from a display case in the mansion during opening hours, was an Abwehr Enigma, a rare type with no plugboard, and with four rotors. A much quoted value was £110,000, which I felt to be something of an overestimate at that time. Was the Trust embarrassed? – you bet, because this machine wasn’t theirs, it belonged to GCHQ.

G312 theft

The machine, serial number G312, made the front cover of the very next issue of Invaluable, a trade periodical devoted to exploring security measures designed to protect art collections, and to tracking down stolen objects when security has failed. BT, then still co-owner of the site offered a £5,000 reward for information leading to its recovery. The grounds around the mansion were searched, the lake was dragged, but to no avail. Machine and thief had vanished. Speculation was rife; many declared it was an ‘inside job’, arising out of rivalries between board members of the Bletchley Park Trust, others argued that it must have been stolen to order for a wealthy client.


It was more than five months later that the Trust received a strange letter, from someone purporting to be in possession of the machine, but wishing it to be returned to its rightful owners. The catch? The writer claimed that an (unidentified) person had bought the machine for £10,000, and would like to be re-imbursed for what he had innocently paid out. Words like ‘ransom’ and ‘blackmail’ would come into most people’s minds at this point.


The Trust and the police worked closely on the case. The ransom wasn’t paid, but the blackmailer wasn’t traced. He grew more demanding, leaving threatening voice mails for the CEO of Bletchley Park, and raising his price to £25,000. This the Trust finally agreed to pay – but before any payment was made, the blackmailer posted the machine to Jeremy Paxman, who was the presenter of the BBC 2 programme ‘Newsnight’. The machine itself was unharmed, but three of its four rotors had been removed. The blackmailer threatened to destroy these if the ransom were not paid in full.


By this time communications with the blackmailer had broadened to include messages published in the personal columns of The Times, and a Times journalist, Nick Fielding, became a go-between, relaying messages of various sorts to police and blackmailer. Finally, in October, an antique dealer, Dennis Yates, was arrested in a telephone box making an incriminating call to Fielding. The rotors were recovered later, undamaged.


Yates was charged with handling stolen goods, and blackmail. His case came to court in September 2001, and he pleaded guilty so readily to the first charge that the second was not proceeded with. He was subsequently sentenced to ten months’ imprisonment, but released within three months. The thief has never been identified, but security at Bletchley Park has been stepped up.

Yates Oct 2001

On a number of occasions, I have had a trade stand at the National Vintage Communication Fair, and was intrigued to find that Yates was often there as well. We passed the time of day, but I never felt able to raise with him the subject of G312. However, the last time I saw him at one of these fairs, on his stand he had – an Enigma machine!

Yates 5.13

What a story – theft, blackmail, coded messages, anonymous letters and parcels, and a mysterious buyer – but the complete story has never been told, and now may well be lost for ever, as a Vintage Radio website recently reported that Yates had been found dead in his car earlier this year.

Enigma Machine Visits Skyscanner

Earlier this year, I was invited to one of the UK’s most successful tech companies, Skyscanner, to give a demonstration of my Enigma machine to some of their software engineers. I have found there’s a real interest from ‘techies’ about the Enigma machine story and the Alan Turing connection, and it was a pleasure to be able to share a little about the story, with such lovely people. (BTW if you’re a software engineer and live in California then take a look at my forthcoming Enigma Machine Silicon Valley Tech Tour, and get in touch if you’d like me to visit your company or tech-meet up).

As part of my visit, they made a short video of me explaining a few things about the Enigma machine which you can watch below. Thanks to Skyscanner for having me, and especially to Lisa Venter and Łukasz Suliga for creating the video.



Alan Turing’s Out-tray: cache of letters found

A collection of nearly 150 letters to and by Alan Turing has been found in a neglected filing cabinet in a storeroom at Manchester University. Turing worked at the university from May 1948, when he was appointed Deputy Director of the university’s Computing Machine Laboratory. There was no Director as such, but the Head of the Mathematics Department was Professor Max Newman, a distinguished mathematician who had been a Bletchley Park codebreaker during the war. Newman’s influence on Turing went back to the 1930s, when his lectures at Cambridge had inspired Turing to work on the Entscheidungsproblem, and this led to Turing’s seminal 1936 paper ‘On Computable Numbers’.


The papers which have just surfaced cover the period from March 1949 to 2 June 1954, and thus run right up to Turing’s death on 7 June. I have not yet been to Manchester to see the originals, but I have read the archivist’s synopsis of every one. Despite there being numerous items written after Turing’s trial and conviction for ‘gross indecency’ in March 1952, no reference is made to any of the problems he faced at this time: his trial, the verdict, the hormone injections and psychiatric analysis, the loss of his Security Clearance, etc. In fact, they shed little light on Turing the man, although he does make some admissions as to his dislike of the USA, his lack of skill as a reviewer, and the gap between his writing and speaking styles.


The subject matter of many of the letters testifies to his growing success and reputation as a mathematician. He receives many requests to write papers and books, to speak at conferences, to review papers, to advise other academics and students on research, to supply copies of his own papers (we’re talking here not just pre-internet days, but pre-photocopier, too), and to permit the Manchester University computer to be used to do work for others. Although none of the letters is outstandingly important, their sheer number and diversity demonstrate clearly that Turing was a highly respected mathematician, right at the forefront of the newly emerging computer revolution, whose views were sought by other eminent mathematicians across the world.


The first Manchester computer, the one Turing used, was called ‘The Baby’, but it was superseded by a series of ‘Atlas’ machines, which remained in use into the late 1960s. It is here that I can reveal a connection from my own past. In the 1960s, I was working for a firm of consulting civil engineers, and we wished to design some large asymmetrical suspended road slabs as part of Newcastle’s Central Motorway East. Computer analysis was the best way forward, so we commissioned Manchester University to run our analyses overnight (day-times were reserved for in-house use). Now comes the bit that anyone under 50 will find incredible. We sent our inputs to Manchester, as punched paper tapes, on the train – and the stacks of fanfold computer paper with the Atlas results came back by train the next day. This was the highest of high-tech in the 1960s!


Of course, in those days, I knew nothing of Turing. Having been researching his achievements during the last twenty years, I am now often asked to speak about Turing and his work. In August, it was the Turing Fest in Edinburgh, and in October I am contributing to a 2-day study tour about Alan Turing, organised by the New Scientist.