On not locking the door when you are under the sea.

Entrance to the Channel Tunnel near Coquelles (France)

I always approach the Channel Tunnel with a little trepidation.  Talk about being 20,000 Leagues under the Sea. I recall one time when the train shuddered, the lights blinked, and then the train shuddered to a halt.
And there we were stuck under the sea because the train had broken down.  Now if there were Academy Awards or Nobel Prizes for panic reaction I would win hands down, I started asking other drivers, have you ever experienced this kind of thing before the phlegmatic Brit' reply was a universal, no, which compounded my panic. 

After approx'  15 minutes of this, it feels like 15 years, an attendant arrives, I rush to her, "What is going on?"
"It is alright, sir."
"But what is going on?"
"Well, I don't know exactly, sir, we are trying to locate the problem."
"Good God, what the..."
"It's alright, sir,  Are you a nervous type, sir?"
"Who me, nervous....what makes you think that?"

Move the clock forward and confidence growing on this trip I am in the toilet having a 'Jimmy Riddle' (piddle). I refuse to lock the door, what if I can't get out  (add a sense of claustrophobia to my other neurosis (s). I flush the chain, it doesn't....what it can't be a lack of water supply.  Ah, now, now it works.

Move the clock forward and now we are  seasoned Tunnel users,".... wouldn''t  travel any other way"  I say in that knowing, bloody irritating way, to people who have never used this masterpiece of engineering.

I

Geological profile along the tunnel as constructed. For the majority of its length the tunnel bores through a chalk marl stratum (layer)