James Greenwood
One of the earliest and best-known 'social explorers' was James Greenwood, who in January 1866 spent a night in the casual ward of the Lambeth workhouse. His titillating account of the experience, A Night in a Workhouse, was published anonymously in three successive issues of the Pall Mall Gazette. His revelations about the repugnant conditions at the institution, and the characters who frequented it, caused a sensation and the articles were subsequently reprinted in pamphlet form. You can read the full text here.
In 1906, forty years after his original explot and the aged 73, Greenwood re-lived his adventure in an undercover visit to the Islington casual ward. You can read the full text of his account of that expedition here.
For US readers 
Unless otherwise indicated, this page () is copyright Peter Higginbotham. Contents may not be reproduced without permission.