Next time you go to Bletchley Park, you might want to take a look beforehand at this really clear and simple explanation of how the WW2 German Enigma machine worked.

It’s the latest video in Jared Owen’s series of 3D animations explaining how things work, and it caught my eye because back in the late 1980s (shortly after the demise of the dinosaurs!) I programmed my Phillips P2000C portable* to emulate the Enigma machine. Actually, that’s not quite truthful; I wasn’t that clever. I found a program in BASIC, copied it out and then adjusted it to change things like the number of rotors and plugboard settings.

I remember changing the number of rotors to five, because I was aware that the Enigma machine started as a civilian 3-rotor encryption device for banking and that when the military adapted it, they upped the number of rotors to five.

But hey, you never stop learning! Watching Jared’s video I realise that all these years I’d got it wrong. It isn’t five operating rotors. It’s three operating rotors selected from five. Duh!

Anyway, if you follow through Jared’s description, you begin to understand the enormity of Bletchley’s problem and the brilliance of Alan Turing and the code-breakers working there.

* The Phillips P2000C portable (“barely luggable” would be a better description, if you had shoulders strong enough to sling it over!) was a CP/M machine running on floppy discs, which included a bundled in copy of BASIC. You can see what it was like here. In those days I was fascinated by the U-Boat war and I also created a database of all the U-boats (1,100+) and their history, using an amazingly advanced (for then) database & language program called FMS-80.