It used to be common to use horses in sub-surface mining. The coal mining industry used "pit ponies" to haul coal from the mines and later, as the workings progressed, in the mines themselves. Because of low roofs, steep grades and forced production, pit ponies had to be low set, heavily bodied and sure-footed. The first known recorded use of pit ponies in Britain was in the Durham coalfield in 1750.
Pit ponies were normally stabled underground, coming to the surface only during the colliery’s annual holiday. Typically, they would work an eight-hour shift each day, during which they might haul 30 tons of coal in tubs on the underground narrow gauge railway.
At the peak in 1913, there were 70,000 ponies underground in Britain. In later years, mechanical haulage replaced pony hauls and ponies tended to be confined to the shorter runs from coal face to main road. Probably the last colliery horse to work underground in a British coal mine, 'Robbie', was retired from Pant y Gasseg, near Pontypool, in May 1999.