Ok this is bugging me and I can\'t find the answer on \'nternet.
Poem by Gerard Benson called \'Riddle\' which is currently plastered all over the Underground:
I was the cause of great troubles, yet, resting amongst leaves, I did nothing wrong.
After much waiting I was taken in hand, passed from one to another.
Broken I moved beyond sharp barriers and was cradled in wetness, mashed to pulp.
Soon I entered a dark tunnel where bathed in acids I altered my being.
But what I entered I also altered, bringing light where there had been darkness.
I brought strife where there had been peace, pain where there had been comfort.
My journey ended in the place of corruption but by then I had changed the world.
Any ideas? I thought maybe apples - alcohol?