Codeshare: my trip to Bletchley Park

[RooFlyer]

St Albans has a parkrun, as does any British town or village, really. Naturally, it's a priority for me, and I skip some of the BookCrossing fun so that I can notch up another event, another nation, another statistic on the page.

How are you doing on your Parkrun alphabet? You can get a Z from Zeehan in W Tas.

 

[Bundy Bear]

How are you doing on your Parkrun alphabet? You can get a Z from Zeehan in W Tas.

Zillmere for the Z in Brisbane, I am working for my 2nd parkrun alphabet, Zeehan is a touch too far away from an airport in Tasmania.

 

[SeatBackForward]

Oh nooooo! You rotter! I

It's a reference that sneaks up on, you like a house.

 

[Flyfrequently]

Late to the party @Skyring but enjoying your travels immensely as usual

 

[Skyring]

How are you doing on your Parkrun alphabet? You can get a Z from Zeehan in W Tas.

Nine more to go, and most of them fairly easy letters. I did Zillmere last year, and at the first-timers briefing the volunteer looked around, "Ah, any tourists here?"

Most of the attendees were tourists, as it happened, and we were only there for one reason.

I'm kind of sorry I didn't take this up years ago during my years of serious travel. Not to worry, there are more important things in life than accumulating some of the sometimes frivolous challenges of parkrun.

 

[Skyring]

Zillmere for the Z in Brisbane, I am working for my 2nd parkrun alphabet, Zeehan is a touch too far away from an airport in Tasmania.

There are a couple in the Netherlands. They could be easier to get to …

 

[Bundy Bear]

There are a couple in the Netherlands. They could be easier to get to …

There is a new parkrun just outside of Amsterdam and a friend in a running group chat suggested I could fly there for the weekend, another Z

 

[Skyring]

A few words about the BookCrossers. That's most of us above. There were a hundred all told, but some weren't present for the final group photo. Together we ransacked all the bookshops in town, and there are some excellent examples in St Albans, then just after the photo was taken, we cleared the hall and set off on a "release walk" setting free books that hadn't been taken from the book buffet tables or were intended for wild release.



If you see a bag or a backpack, it's full of books.





As noted earlier, St Albans is a remarkably pretty town, um cathedral city. Charming houses, shops, pubs, and parks abound. We walked around much of the old town, our guide making remarks about "herding cats" as we paused to leave books in likely – and unlikely – spots, photograph same, and pause here and there to read historical plaques, photograph same, say hello to passing dogs and ducks, photograph same, and so on until we fetched up at the Clock Tower, the symbolic centre of the town.



Those with keen eyes may be able to spot a book here and there in the landscape. My AirBnB is just out of sight beyond the right side of the Clock Tower and the building on the right with the vegetated eaves is The Boot pub, quite popular at all hours.



A glimpse of my bay window beside the scooter sign but I really wanted to highlight the plaque marking the site of one of Eleanor's crosses nearly 750 years after her death. Her grieving husband, King Edward I, erected a series of ornate monuments to mark the nightly resting places as his wife's body was carried from Nottinghamshire to Westminster Abbey. Three of these survive more or less intact, and there is a well-known reproduction of the final memorial at Charing Cross, which owes its name to the since destroyed Eleanor Cross that graced the long-since-engulfed village of Charing.

This was pretty much our final stopping place as well. More BookCrossers began their journeys home, and we latestayers went off to enjoy a traditional Sunday roast at a nearby pub, which also happened to be hosting a Beer and Cider festival.



My pub grub above, including a fluffy boulder of Yorkshire Pudding, two generous slices of perfectly tender beef, and a pint of local cider.

We enjoyed a long, lazy lunch before heading off for a welcome cone or tub of icecream in the summer afternoon, and dispersing to pack or nap or browse yet more bookshops. Or all of the above. I think one or two gathered for yet another meal, but I was full of food and drink and I needed to prepare for the day ahead, where I would pack up, look through a few places in London with my mate Swen, and we'd then board our flights at Heathrow for home. A couple of hours for Swen, three days for me.

 

[Seat0B]

That roast is certainly classic - what a monster of a Yorkshire Pudding!

 

[Skyring]

OK, one last thing about the BookCrosser convention. One of the organising crew had made a themed puzzle – codebreaking, kind of – the answer of which was the name of a book by a best-selling local author. A challenge, but I could see myself spending half an hour of research on this.

"Please solve this puzzle, Claude," I said, taking a snap of the sheet with my phone.

Got it. The letters spell out row by row:

Row	Clues → Letters	Word
1	Life of Pi (T) · New Zealand (H) · Texas (E)	THE
2	This Book is Gay (W) · Arthur Ransome (R) · Texas (E) · Ulysses (C) · Kurt Wallander (K)	WRECK
3	The Hate U Give (O) · Nebraska (F)	OF
4	Life of Pi (T) · New Zealand (H) · Texas (E)	THE
5	Orange (Z) · Edinburgh (A) · 27 million (N) · Orange (Z) · Daisy Dalrymple (I) · Jura (B) · Edinburgh (A) · Arthur Ransome (R)	ZANZIBAR

The mystery title is The Wreck of the Zanzibar.
A few of the neater bits worked into the clues:

• "Most registered book on BookCrossing" → Life of Pi — fitting, given how heavily that one's travelled through OBCZ circles.
• "Station named after a novel" → Edinburgh, home of Waverley Station, named for Walter Scott's Waverley.
• Arthur Ransome does double duty: he wrote We Didn't Mean to Go to Sea (kids not meaning to go to sea) and, separately, was the journalist who knew Lenin and moonlighted for British intelligence

Nicely built puzzle for a bookcrossing crowd — hope the St Albans convention's going well, and here's hoping your bag's turned up by now!

***
I can see AI becoming an increasing part of everyday life, solving ever more complex life puzzles. It's scary, really. I can see us all being devoured by this monster.

It's also kind of relevant, given that Alan Turing was the star genius at Bletchley Park – the "Turing Test" used to determine if computers have reached a certain level of intelligence (i.e. ours) was an idea he came up with – and that the first computer, the Colossus machine, was built there. I wonder how long Claude would take to crack Enigma?

OK, bit of a curly one, Claude. How long would it take you to crack the Enigma code in various circumstances?

***

Good change of pace! The honest answer is "it depends enormously on what you mean by cracking it" — the naive brute-force number is basically meaningless, and the interesting answer is about which shortcuts are available.

Brute force, no shortcuts at all
A 3-rotor Enigma with plugboard has a keyspace around 10^23 for a single day's settings (rotor choice, ring settings, plugboard pairs, starting positions). Even with serious modern computing that's not something you knock over by trying every combination — this was never really "crackable" this way, then or now.

With a crib (known or guessed plaintext)
This is how Bletchley actually did it. If you know or can guess a stretch of plaintext ("wettervorhersage" turning up at the start of German weather reports, say), the menu-and-loop logic the Bombe used eliminates most of the plugboard search almost immediately, because Enigma never maps a letter to itself. Given a decent crib and a working Enigma simulator, I could write the code for this myself right now, and depending on message length it'd likely run in seconds to a few minutes on ordinary hardware — nothing exotic needed.

Ciphertext only, message is long enough, rotor wiring known
No crib, just the coded text. Modern hobbyists and academics do this with hill-climbing / simulated annealing against letter- and trigram-frequency statistics — essentially the same statistical intuition Turing and Alan (I.J.) Good used, automated. It generally needs a few hundred letters of ciphertext minimum to have enough statistical signal, and then it's a search over rotor order, ring settings, and plugboard that converges in minutes to an hour or so of compute. Short messages (a hundred letters or less) usually defeat this approach outright — not enough signal.

Ciphertext only, rotor wiring itself unknown
Now you're doing what Rejewski's team at the Polish Cipher Bureau did in the 1930s — reconstructing the internal wiring from patterns in intercepted traffic before you can even start on daily keys. That's a much deeper mathematical problem (permutation group theory on indicator doubling, in their case) and not something that falls out of a quick script.

What actually broke it historically
Not brute force — cribs from predictable message formats, operator laziness (repeated settings, lazy plugboard choices), captured code books, and known procedural flaws (like never plugging a letter to itself, and the early indicator-doubling bug the Poles exploited). Bletchley's edge was less "faster computation" and more "smarter reduction of the search space."

So: give me a crib and I can probably solve it in front of you in a couple of minutes using the code tool. Give me only a longish ciphertext and I can likely still get there with statistical hill-climbing, just slower. Give me a short ciphertext with nothing else — that's genuinely a hard problem, and honestly beyond what's practical without more information, same as it was for the Germans' adversaries at the time.

Keen to actually see it done? I could knock together a working toy Enigma + crib-based solver as a demonstration if that'd be fun.

***

Fun? For whom?