Code 1: Blood
Code 2: Urine/faeces
Code 3: Vomit
If you thought NASA owned the only 'vomit comet' you would be wrong as many Londoners can't even cope with a tube journey late at night without puking. I bet the tube's network of hard-working cleaning staff can wait for the night tube! It makes going out in London so much more accessible but it will be a Code 3 nightmare.
Code 4: Spillage
Yep, if blood, piss and vomit don't cover it, it's a Code 4. Got a dodgy lid on your coffee and managed to throw it all over yourself, the platform and the back of the man in front? Quick – shout CODE 4 as loud as you can. We need to get rid of that slip hazard ASAP – health and safety, people!
Code 5: Broken glass
Who is it going around smashing all those windows? But wait, there aren't any – it's called the Underground, duh. Broken glass is a tube code, so it must happen. Maybe it's for when very refined Londoners bring their champagne picnics on the tube and get so excited on the bubbles that they cheers so hard they smash their glasses. Whatever it is, be careful in open-toed sandals if you hear Code 5 over the loudspeaker.
Code 6: Litter
All those poems on the Underground are telling us not to litter but it's difficult when there are no bins. Littering is bad for the environment and tube cleaning staff. With thousands of discarded daily newspapers to deal with, let's try and be nice and think before you leave that banana skin or empty Coke can under your seat because that is a Code 6. Bin liners at the ready!
Code 7: Everything else
Ooooooh, mysterious. Code 7 is for anything that isn't covered in the first six codes. Do you think the fashion police are covered by Code 7? Manspreading? Celeb spotting? Wait, maybe this is the code for Daniel Craig on the tube! Ladies, listen out!
Fire. You may have heard 'Would Inspector Sands please report to the operation room' over the speaker on the tube or at a rail station, which means 'grab the sand buckets, there is a fire'. Now you know the true meaning, you will find that it happens more than you think. If you hear someone calling for Inspector Sands, head for the exit pronto, or just look smug because you are totally in on the tube codes and can carry on with your journey.