Been on the tube/metro/subway lately?
Then you have this chap to thank. James Henry Greathead (the original bighead!) was the chief engineeer of the City and South London Railway and inventor of the travelling shield. This was the device that permitted the deep underground tunnels to be dug. Here is a Wikipedia article on them - you will see that most tunnels built today are still loosely based on his design. When? Well, the first line opened in 1890. I'm not certain I'd enjoy a steam train running deep underground, but that's what they did.
He lives these days near Bank, at the top of Cornhill.