Jack London 
The People of the Abyss 
Jack LONDON Novels

But you can’t do it, you know, ” friends said, to whom I applied for assistance in the matter of sinking myself down into the East End of London. “You had better see the police for a guide, ” they added, on second thought, painfully endeavouring to adjust themselves to the psychological processes of a madman who had come to them with better credentials than brains.

“But I don’t want to see the police, ” I protested. “What I wish to do is to go down into the East End and see things for myself. I wish to know how those people are living there, and why they are living there, and what they are living for. In short, I am going to live there myself.