London Blog

The Scientific Tourist In London: #10. The Pedestrian Crossing of Doom

What’s the most famous pedestrian crossing in the world? Probably, this:

Yes, the Abbey Road zebra crossing, made famous after the lead singer of Wings, one of the Travelling Wilburys, Yoko Ono’s husband and the voice of Thomas the Tank Engine (once, collectively known as The Beatles, I’m told) decided to feature its tarmacadamic striations on their final proper album.

But there’s another pedestrian crossing in town with less frivolous claims to world attention. Here it is:

We’re on the corner of Southampton Row and Russell Square in leafy Bloomsbury. There’s no plaque to mark the event but this is the unlikely spot where the nuclear chain reaction was first conceived.

Hungarian scientist Leó Szilárd was a theoretical physicist working in Berlin. His credentials were excellent, having trained under Planck, Einstein and von Laue. But the forces of Nazism were on the rise and in 1933 the Jewish Szilárd fled to London to escape possible persecution. Our great city was quick to inspire him. On the morning of 12 September 1933, Szilárd was waiting at this crossing for the lights to change, mulling over a recent speech by Ernest Rutherford who’d dismissed the possibility of atomic energy as ‘moonshine’.

As he stepped off the kerb, so the story goes, Szilárd was hit by an idea (and not by the number 59 bus, which might have happened were he to absent-mindedly cross at the time of my photo). Perhaps it was the momentary alignment of vehicles, or the jostling of pedestrians eager to get across the road. He began to think about the power of collisions. If a nucleus could be hit by a neutron to force the release of two further neutrons, and then each of these could go on to instigate similar ejections from other nuclei, a chain reaction would ensue that would liberate huge amounts of energy. In other, slightly hyperbolic words, Szilárd had invented the atomic bomb.

While the humble street crossing was an unlikely place to make one of the most important imaginative leaps in human history, the idea’s first practical implementation occurred in an equally unusual setting. On 2 December 1942, Szilárd and other scientists watched the first ever self-sustaining chain reaction in a squash court beneath the athletics stadium at the University of Chicago.

Two and a half years later, (and to Szilárd’s horror) a quarter of a million Japanese citizens were dead in the wake of the atomic strikes on Hiroshima and Nagasaki. Szilárd’s brainwave, initiated by the chance movements of cars at a Bloomsbury pedestrian crossing, had led to a weapon of unprecedented power.

And thus did the gentle streets of Bloomsbury, home to Virginia Woolf, Dorothy Sayers, Charles Dickens and William Butler Yeats, also inspire that darkest of eras, when the world hovered only a button-press away from mutually assured destruction and nuclear holocaust.

Previous instalments of the Scientific Tourist in London.


  1. Report this comment

    Bob O'Hara said:


    The only sudden moment of scientific inspiration I ever had struck me when I was walking past the sink in our lab. It was all to do with immigration in mildew.

  2. Report this comment

    Kate Grant said:

    Where do you get these wonderful nuggets of information from? I just get “oh, damn! just missed the No. 59 bus” moments…

  3. Report this comment

    Chris Surridge said:

    Matt, you ought to make a map of your tourist spots. This one is here I believe.

  4. Report this comment

    Matt Brown said:

    Cheers all.

    Kate – it’s my job to know everything about London. 😉

    Chris – yup, that’s the spot. I did start making a map of these (maps is what Matt’s do best). However, is you can’t embed Google maps in NN there didn’t seem much point. It is possible with MT4 though so, touch wood, the next instalment will include a map of all locations.

  5. Report this comment

    Brian Clegg said:

    It’s great to see this, Matt – I wrote about it a few months ago in a book I’ve got coming out in the autumn, but only had a vague image in my head of where it was (I suppose I should have looked on StreetView, really)…

  6. Report this comment

    Brian Clegg said:

    P.S.Doesn’t Let it Be count as a proper album?

  7. Report this comment

    Eva Amsen said:

    The Beatles crossing itself also has a science connection, by the way. The authors of Molecular Biology of the Cell pose there on the back cover of one of the editions. (Larry Moran has the picture op on his blog here )

    I think I have the edition with this image on it, but everything is in moving boxes still, so I’ll probably see it next around the time MT4 comes out =P

  8. Report this comment

    Matt Brown said:

    So they do, Eva. Had forgotten about that.

    Brian: Yes and no. Let It Be was mostly recorded before Abbey Road, but released afterwards. It feels more complete and rounded, while Let it Be sounds like a ragtag collection of (good) extra material. And In The End…I think Abbey Road has a strong claim to being the last ‘proper’ album.

  9. Report this comment

    Richard Wintle said:

    Ringo once played the Mock Turtle in a TV adaptation of Alice In Wonderland, too.

    Matt – fabulous piece of history. A bit depressing though, in a way.

    [off to read the other nine episodes]

  10. Report this comment

    Stephen Curry said:

    Fabulous post Matt. Szilard appears (at this crossing) on the very first page of Richard Rhodes’ wonderful The making of the atomic bomb, which gives a superb history of 20th century atomic physics and the Manhattan project. It’s one of my all time favourites.

    But I was surprised to find him later chatting to Jacob and Monod in Paris in the early days of molecular biology, which he turned to in 1947 (according to Horace Judson’s Eighth Day of Creation, another brilliant book.)

  11. Report this comment

    Mike Paterson said:

    Very interesting. Can anyone tell me where I could find a transcript of Szilárd’s own account of the moment?

  12. Report this comment

    Richard P. Grant said:

    I just looked him up on Amazon and there’s a biography… for over a hundred quid!!

  13. Report this comment

    Matt Brown said:

    Thanks all. I’ve not seen a transcript of Szilard’s own account, but all reports tell it the same so I presume it’s based on an original source somewhere.

  14. Report this comment

    Ian Brooks said:

    Off topic perhaps, but it has irritated me as long as I can remember (not as long you’d think) that the Lead Singer of Wings is out of step with the rest of them. I am OCD.

  15. Report this comment

    Ian Brooks said:

    Off topic perhaps, but it has irritated me as long as I can remember (not as long you’d think) that the Lead Singer of Wings is out of step with the rest of them. I am OCD.

  16. Report this comment

    Matt Brown said:

    You know about the whole ‘Paul is dead’ thing, right, Ian?

  17. Report this comment

    Kristi Vogel said:

    @ Ian – Note that Paul is also the only one who is barefoot, and he’s holding his “last cigarette”. John is in white, a funeral/death color in some cultures. But you knew all that already.

    [/too much Beatles trivia in hippocampus]

    Awesome post, Matt!

  18. Report this comment

    Elizabeth Moritz said:

    I smile anytime I see/hear someone mention the Travelling Wilburys. Used to call them the Wilberries listening to them as a kid with my dad 🙂

  19. Report this comment

    samantak p said:

    It’s really interesting.

    Awesome post, Matt!

  20. Report this comment

    foundatijack smith said:

    I like this story very much because totally news in this article very very trully. Scientific Tourist is very very useful for us country.

    Force Factor

Comments are closed.