Young Londoners not in the know may well be using contactless for the odd journey here and there thinking it may not be worth their time investing in travel cards when they are not using the travel system too often.
One student online told of her newfound discovery in being able to travel the system a lot cheaper – but did say she didn't "want to think about" how much she had wasted over the years.
She said: "Since finishing my degree I did not travel enough to warrant buying travelcards with the Oyster 18+ discount, so have just been using contactless on my card as it says there is no discount on pay as you go with the 18+ oyster.
"However... with a 16-25 or 26-30 railcard, there's 1/3 off off-peak fares and daily caps.
"I never considered that my student oyster not offering me a discount would mean I could still get a young persons discount with a different card as why wouldnt the student card access that discount?!
"Anyway, I cringe to think of how much I've thrown down the drain over 3 years, wanted to highlight this to hopefully ensure others don't make the same mistake!
"Also I've had the required railcard the whole time, just only ever used it on trains, eurghhh."