A while ago (maybe even a few years ago) I was given a Bletchley Park mug that is black when cold. When it heats up (from having a hot drink inside it) it turns white and reveals a sequence of pictures and a message about Bletchley Park at the top.

It was given to me as a gift by my brother after he'd visited the Bletchley Park Trust/Museum some time ago (years but not decades). It was sold at the gift shop there. I never really looked at it in detail before but I brought it into work today and when I looked at what the heat revealed I noticed the code. To add context Bletchley Park is where the UK code breakers who cracked the German Enigma Codes during World War 2 worked.

At the bottom is a sequence of letters:


This isn't a simple shift cipher (I checked for that) but the general letter combinations and suchlike look valid for it to be a coded message of some sort. It's been a long time since I did any code cracking and this sample isn't really long enough or containing any double letters for the tricks I vaguely remember to work.

It does seem suspicious that it is blocks of 5 characters in each "word" apart from the last 2 so the spaces could well be misleading.

Given the context of where the mug came from I wouldn't be surprised to find the phrases "Alan Turing" or "Bletchley Park" and/or "Trust" in the translated text somewhere.

Is anyone able to decipher it?

(Note that it is most likely in British English)

The mug cool: enter image description here

The mug hot

enter image description here

enter image description here

enter image description here

  • 4
    $\begingroup$ None seem to be correct answers, but running the text through the crypto solver at rumkin.com gives some amusing results. Poor Edith. $\endgroup$
    – Irishpanda
    Dec 7, 2015 at 14:22
  • 2
    $\begingroup$ Most likely an Enigma ciphertext, but without further information or context... well, not really feasible. $\endgroup$ Dec 7, 2015 at 14:48
  • 5
    $\begingroup$ The M1322 is the serial number of the Enigma in the Bletchley Park Museum. An photo from 2014 shows the machine with the information that the rotors II, IV, V and reflector B were used. However, all this could also lead in a totally wrong direction. $\endgroup$
    – Sleafar
    Dec 7, 2015 at 21:25
  • 3
    $\begingroup$ Splitting text into 5-character blocks for ciphering and deciphering was standard practice in the 30s/40s, so apart from confirming that it's intended to be understood as ciphertext there's no significance to the spaces. $\endgroup$ Dec 8, 2015 at 11:09
  • 5
    $\begingroup$ Your parents' mug would have the same code. It's the same code on the mouse pad Bletchley Park had for sale at the time, and it had the same pictures and text as on the mug. I found that using the Wayback Machine (sorry, I'm unable to access it now to provide a link) for the gift shop site, and the description for the mug just mentioned that there was a secret to be revealed. The place's slogan, "Britain's Best Kept Secret" fits the number of encoded characters, but it can't be the phrase if the code is a true enigma cipher because a letter can't encode to itself. $\endgroup$
    – Mythi
    Dec 10, 2015 at 19:57

1 Answer 1


Over the weekend I emailed Bletchley Park to see if they could shed any light on it. Today I got this reply:

Dear Tim,

Thank you for your email which was circulated, we believe the letters are random. However we have sent your email onto our Education and Learning department for further information, until then unfortunately we don't have any further information. If there are any findings or developments will contact you in the first instance.

Kind Regards,

Bletchley Park Information

So it seems that there is no code to solve :( Very disappointing.

If I hear anything different I'll update. Sorry to have wasted people's time.

  • 3
    $\begingroup$ Well, a negative result is also a result :-) $\endgroup$ Dec 17, 2015 at 14:56
  • 1
    $\begingroup$ atleast i found out about the origin of enigma and learned some history. Thanks for that. $\endgroup$
    – manshu
    Dec 17, 2015 at 18:38
  • $\begingroup$ Weird, I emailed them as well, but never got a response. $\endgroup$
    – Irishpanda
    Dec 18, 2015 at 15:34
  • $\begingroup$ It took them quite a while to reply to mine, I emailed at the weekend and got the reply yesterday. They were probably trying to find the answer. $\endgroup$
    – Tim B
    Dec 18, 2015 at 15:36
  • 2
    $\begingroup$ Well, that's a disappointment. One would've hoped Bletchley Park of all places could put more effort into their enciphered messages. $\endgroup$ Oct 15, 2016 at 15:46

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