These people really are unbelievable.
I went to Bletchley Park, and thankfully didn't come across Colossus until after lunch. Otherwise I'd have starved my children. I've not done it before or since but was so impressed, that I gave all my money as a donation.
I met this guy there, it was like a scene from the Val Kilmer film, "Top Secret" where she describes building a rudimentary shelter from palm fronds and snot, except he built a Colossus, Tommy Flowers like, from the remains of BT's aging electromechanical telephone exchanges.
I truly recommend every adult go there, but don't take your kids until they're old enough to understand how close we came to losing.
It was the best day out I've ever had. Made Al Ambra look like a day out at burger king. We truly owe these people, and all those who provided the data, our entire existence.
(and it can be an historian, it depends on how you say it. If it's to be said "An 'istorian, gallic fashion then it is spelled "An historian." and you drop the aitch, and if historian is pronounced with a hard "H", then it's "A historian" - both are valid British English, so far as I'm aware.)