This episode of the show is brought to you by listeners like you, who with a small contribution help to fund the podcast.

Go to Patreon.com forward slash W W2 podcast for details on how you can help support the show.

Hello and welcome to another World War II podcast. I'm Angus Wallace. In this episode we'll

be looking at the attempts to disrupt and destroy the Germans access to

heavy water which was essential for their atomic research.

If that sounds familiar, it could be because you've seen the film The Heroes of Telemark

or watched one of the many documentaries on the operations against Heavy Water Plant at Vermog.

But very few of these documentaries will have looked at the subject as closely as Neil Baskam's new book, Winter Fortress.

Painestakingly researched with access to the diaries of some of the men involved,

it sheds light on a remarkable series of operations in Norway.

Neil, thank you for joining me. We need to start with

heavy water to understand why the Allies were so keen to sabotage the German efforts in making it.

Why was it important?

Well, having water is, you know, I don't necessarily need to go into the deep physics of it but essentially

hydrogen has a single proton and a single electron and heavy hydrogen has a neutron actually in the nucleus as well, which increases the weight,

which is why we call it heavy hydrogen.

Another name for that is D2O, which is heavy water.

And the amount of heavy water in regular water is almost imperceptible.

It's one molecule of heavy water for every 41 million molecules of regular water.

So it's very rare in nature and it's very hard to isolate and produce in any

quantity. And the reason that heavy water is important in nuclear research and in the construction of potentially an atomic bomb is it acts as a moderator.

What that means is in a nuclear reaction, in a

...