Slippery When Wet

Ok, so in other train related news, what on earth is going on when a
train station built in the centre of London has to shut some of it's
entrances when it rains?

The ever lovely Charing Cross had a whole entrance closed and another
on some bizarre one-way system tonight because the floor was slippy.

Are we insane? Does this happen everytime there's a bit of drissle?
And how do you spell drissle?

Enquiring minds need to know. And yes, I am on the old iPhone on the
train.

Again.