[hi_hi]

You can't talk about hobby tunnels without mentioning the Moleman of Hackney :-)

- https://en.wikipedia.org/wiki/William_Lyttle

- The house was later brought back to life in an amazing way https://www.vogue.co.uk/arts-and-lifestyle/article/sue-webst...

[Nursie]

That is fascinating!

But I feel he was an amateur compared to Joseph Williamson :)

https://en.wikipedia.org/wiki/Williamson_Tunnels

[hi_hi]

Brilliant. This indeed wins :-)

[elihu]

Also worth mentioning Baldassare Forestiere, who spent about 40 years digging an extensive network of tunnels in Fresno, CA.

https://en.wikipedia.org/wiki/Forestiere_Underground_Gardens

[jacquesm]

I haven't seen the Public Image Ltd logo in a very long time.