Beneath the streets of London, a mystery gas kills four sewer workers

Four men working to clear obstacles and repair brickwork in the London sewers under the area of the Old Bailey failed to re-emerge.  A search found them all dead of suffocation along with a large number of rats.  The type and source of the gas were not known but it was not explosive as the men's open lamps were still burning and only filled the area where the victims were found. (By John Osborne)