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From Wondery, I'm Tristan Donovan and this is the Spy Who.

I'm one of the executive producers on The Spy Who and usually I'm part of the team behind the scenes.

Usually I work on the scripts but today I've been taken out of the safe house to try and find out more about our latest story.

That story of course was the spy who saved MI5, the tale of Oleg Lelen.

His information led to the biggest expulsion of Soviet spies by any Western government during

the Cold War. MI5 regarded as an important turning point in their battle with Soviet intelligence.

This was a tricky one because the full story is still locked away in MI5's vaults.

So we had to go through old newspaper articles, books, archive material and piece this together

bit by bit. And it's a story with lots of parallels today, with hundreds of Russian spies who

have been expelled from European cities following the invasion of Ukraine.

But Leland's story wasn't just about getting rid of spies, it was also about rehabilitating

MI5. In this episode, we're going to explore why MI5 was in the doghouse as the 70s began, and with me to discuss it is Andrew Loney, author of Stalin's Englishman.

Hello, Andrew.

Hello.

Thanks for joining us.

Pleasure.

So, before we get cracking, in a few words,

how much of an impact would you say the Cambridge spy scandal had on British intelligence

and even Britain itself?

Well, I think it had a huge impact, and we're still seeing the impact to this day.

I mean, it created a witch hunt, basically, within MI5. So it really sowed seeds of discord

...