Another interesting story.

Knew there were tunnels in West Berlin aiding escapers from East Berlin but never heard of tunnel 29.

Anyway here is the story:

https://www.bbc.co.uk/news/extra/Od4dL9Lip2/tunnel_29


Dirk

This tunnel was dug in the reverse direction by the CIA and SIS, with the intention of tapping into the landlines of the Red Army in Berlin.

Berlin Spy Tunnel

What the link above doesn't mention was that Operation Gold, as it was known, was compromised from the beginning as SIS had been penetrated by KGB agent George Blake. Though to protect their source the KGB did not inform either the Red Army's security, the GRU or the East German Stasi.