Holwell was a survivor of the Black Hole of Calcutta in Fort William, Calcutta , a poorly ventilated dungeon measuring 4.30 × 5.50 ⁠metres (14 × 18 ⁠⁠feet), in which troops of Siraj ud-Daulah, the Nawab of Bengal, held British prisoners of war the night of 20 June 1756. As a result of this incident there were supposedly many deaths from suffocation and heat exhauston. Howell's account of this incident  obtained wide circulation in England, and some claim this gained support for the East India Company's conquest of India. His account of the incident was not publicly questioned during his lifetime, nor for more than a century after his death. However, in recent years, his version of the event has been called into question by historians. Digital facsimile from the Hathi Trust at this link.