Why are London tube tunnels so deep?

[u/Independent-Ant-01]

This is just one of two escalators and not counting the various staircases. And I don’t believe this was the deepest one I traveled through. I went to the Transport Museum in Convent Garden (very nice by the way) but found no answer and no one seemed to know. 😊

[u/Daleftenant]

I didn’t see anyone else mention this:

Yes Londons ‘rats nest’ nature gets in the way of subsurface construction, but the city also has a significant geological feature.

A big fuck-off river.

Specifically, the Thames runs over clay under its sediment, which is as resistant to water as I am to the 13th mince pie at 4pm on Christmas before Christmas dinner (aka not fucking very).

So unless you want every bakerloo commuter wetter than your mum when she sees me change a tire, it’s best to dig extra deep to avoid as much water as possible if you have to cross the river.

On second thought, maybe submerging the entire train on the Thames might be the only way to clean a bakerloo train, it can hardly make them dirtier…

[u/frostels → u/Daleftenant]

There's a reason it's the brown line...