There's a report in the Leic Chronicle of 7 Jan 1871. It's quite a long report so I can't copy it all out but basically this is the gist of it:
"Singular death of a goods guard"
Inquest held on Mon 2 Jan in the parish of St Margaret by J Gregory Esq, coroner, on David Bosworth, about 27 yrs old.
John Robotham of Stretton nr Burton was deceased's father in law.
Engine driver Joseph Green gave evidence; David B was guard on a train carrying barrels of beer from Burton to Wellingborough. They did the reverse journey early in the morning; the train stopped at wigston then at Knighton Junction and the driver became alarmed when there was no sign of the guard. He knocked down the door of the "break" and David was found sitting in there; he took one breath but no others. He had made himself a coal fire in a tin grease box in the break and there was a strong sulphurous smell. (It had been an "intensely cold" night).
The doctor felt cause of death was as follows:
"apoplexy caused by his eating a hearty supper and afterwards leaning over the fire in his van. Deceased appeared to have a short neck and full habit of body which would predispose him to the attack".
Coroner's verdict "apoplexy" and the jury "suggested the desirability of some ssafe an for warming the guards' breaks in inclement weather".
From the sound of it he probably died of carbon monoxide poisoning in his attempts to avoid hypothermia
