A small dark grey MG sports car pulls up to the gates inside the Harwell Nuclear Energy

Research Centre. The driver gives a familiar nod to the security guard in the box and

the gates ring open. At the wheel is a atomic physicist, Klaus Fuchs. Next to him, his friend

and boss, Herbert Skinner. They drive down an oxygen-country lane, carpeted in golden

leaves, on their way to a meeting at the General Electric Company on the outskirts of London.

Does Klaus Fuchs notice, in his rearview mirror, when another car slips out of a lay-by and

starts to follow them? Does he register the three men inside the car?

Back to that evening, when Fuchs returns home, having said goodbye to Skinner. Does he suspect

that there are people listening to his every movement? As he stokes the fire, or prepares

his dinner? When the phone was put back on its cradle, it didn't cut off. That allowed

them to hear whatever was being said in the room. In both his office and his home, they

also looked at his mail, they checked for it in visible ink, they checked everything they could.

And when, later in the evening, there's a covert knock on the door, the unseen audience listens

as Fuchs gets up and lets him his female guest. What they say to each other isn't clear,

but it is clear that they both retire to the couch. The listener records that Fuchs stokes the

fire and that the woman makes the occasional murmur. MI5 are learning very little about Klaus Fuchs's

atomic espionage for the Soviets, but they are now privy to the affair he's having with Ernest Skinner,

the wife of his boss. From the BBC World Service, I'm Rosar Ellis, and this is season 2 of The Bomb.

Episode 8, The Uncertainty Principle

The chain of events that led MI5 towards their target,

as much to chance and to human error, but none of it has been Klaus Fuchs's error.

In the end, it's the Russian intelligence services that let him down.

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