From Austerlitz, a novel by an author I fell in love with this summer, W.G. Sebald (finishing Austerlitz, which happened this weekend, also meant finishing all of the books published during his life—he died in 2001):

Then we walked the rest of the way in silence, going on downstream from Wapping and Shadwell to the quiet basins which reflect the towering office blocks of the Docklands area, and so to the Foot Tunnel running under the bend in the river. Over on the other side we climbed up through Greenwich Park to the Royal Observatory, which had scarcely any visitors apart from us on this cold day not long before Christmas.
I walked through that tunnel in 1988. And the reason why I remember the experience so vividly is because it was there (somewhere in the middle) a white man begged me for money. At the time, I was very new to London and, because I had lived 8 years in Southern Africa, had completely forgotten that people who weren't black could also be desperately poor. When the white man asked me for money, I froze on the spot and looked at his skin, trying again and again to match it with the words coming out of his mouth. In a state of shock, I gave a coin, and this shock (which the white beggar failed to notice) was increased by the thanks he gave me for it. He wasn't joking! He really needed the money! He took money from a black man! A whole month was required for me to properly absorb the fact that in the West, white people could be as poor as black people.
  • The Book and the Battle