The London Underground is a lot like a 007 spy movie: there are hidden entrances (under the Houses of Parliament), secret codes and Daniel Craig (well, he is British; he must have taken the tube once). You will have to find Daniel Craig on your own but we can help with the secret codes bit. Here are eight London tube codes you would never know the meanings of unless you watched that documentary series on the tube and wrote them all down. They have called most of them 'code', so it's not like they are trying that hard on keeping it a secret.

Code 1: Blood

Code 1 is announced when someone has lost some of the red stuff, be it in injury or a lady pants related situation. This code can most often be heard on October 31 when there is fake Code 1 all over the place. Many members of tube staff also use it in the place of a common profanity: 'Oh Code 1'y hell, Margaret, I forgot to tap out at Highbury & Islington.'

Code 2: Urine/faeces

Blood is one thing but going to the toilet on the tube is a whole other story – and we are not just talking number one, as Code 2 covers a number one and a number two. It seems some Londoners get over-excited or caught short and can't help doing a Code 2 on the tube. And many people just can't seem to get to grips with the fact that the tube is not National Rail and there aren't toilets on the trains. 'Alan, you've Code 2'd in the stairwell and the splash-back has contaminated my oyster card AGAIN. No Alan. That's a Metro, not a human litter tray'.

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!

Inspector Sands

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.

Check out 25 more things you didn't know about the tube.

Share the story