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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.

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.

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.

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.

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.

CNET getting hands on with the Enigma Machine, San Francisco HQ, Feb 2018

Speaking at CNET HQ, San Francisco, Feb 2018

Invited to speak at Facebook HQ, Silicon Valley, Feb 2018

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.

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.

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!

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.

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.

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.

What a spell-binding film but what a travesty! To make the story even more dramatic than real life, director Morten Tyldum introduced numerous distortions. The website Information is Beautiful analyses 17 films which claim to be based on true stories, scoring each scene according to how true it actually is.

Of the 17, ‘The Imitation Game’ comes a miserable bottom, with a truth rating of only 41.4%, way below any of the others.

One part that was accurate however, was the depiction of the Engima machine that was shown in the short U-boat scene. I know this because it was my 4-rotor Enigma machine that was used in the film!