"was never displayed in a single English tube station"

Commerce The Awl has a massive post charting the copyright snarl up surrounding "Keep Calm and Carry On". That's all worth reading, but in typical style they've also included a section explaining the origin of the original poster:

"The Keep Calm and Carry On poster was designed and produced by the British government in 1939 in advance of the war, but it was never displayed in a single English tube station or tobacconists or newsagents. Not one ordinary citizen ever saw it in the street before or during the war.

Of the 2.5 million posters originally printed, only a handful survived the war; all the rest were pulped. Exactly two copies are known to have made it into private hands. One of these is owned by Wartime Posters of Warrington, Cheshire. The other is Stuart Manley's."

The examples on the post of posters that were actually utilised demonstrates that sometimes someone can create something and not see its potential value.