Before 1872 there was almost nothing here. Three farms - Twyn-y-Garreg, Pantanas, Cefn Forest - and the quiet River Taff Bargoed running down a wooded valley between the slopes. Then Frederick W Harris and his backers signed a mineral lease over three thousand acres, and the valley changed. Construction of the main shafts began in October 1872, sinking in February 1873. The work was punishing - water gushed into the shafts continuously, and the operation needed pumps running every day of its life to keep the workings dry. The 167-strong sinking crew was not always paid on time. Seven men died before the pit produced its first ton of coal. By May 1878 the company had spent over 300,000 pounds. The two shafts stood 180 feet apart, one sunk to 649 yards, the other to 760 - a depth that made Deep Navigation, when it finally opened, by some margin the deepest mine in the entire coalfield.

Going down was always the dangerous part. On 12 December 1884, five men descended No. 2 South shaft in a bowk - a heavy iron bucket used for maintenance work - to replace the safety harness. They had barely begun their descent when the 3.5-inch braided steel flat rope above them parted. Four fell to their deaths 700 yards below. The fifth, Thomas John Dobbs, had been guiding the bowk down on a separate rope, and managed to lower himself hand over hand until he reached the pit bottom, where he was rescued with bruises and shock. The inspectors found the rope had corroded where it touched the headframe sheave wheel; the protective coating of tar had hidden the damage. The unusual riveted sheave wheels at Deep Navigation, made of pieces bolted together rather than cast as one, were not replaced until 1961 and 1963. On 11 November 1902, the shaft killed again - a water pipe came loose and crashed onto an ascending cage carrying 32 men, killing five and injuring two. The cages went down and came back up many millions of times. Most of those journeys ended safely. Some did not.

What came out of the pit was extraordinary. Deep Navigation's seams produced steam coal of a quality unmatched almost anywhere in Britain - hard, low in ash, high in calorific value, ideal for ships' boilers that needed maximum heat from minimum stoking. The Royal Navy bought it; merchant fleets bought it; Cunard specified it. When the Lusitania and Mauretania chased the Blue Riband for fastest Atlantic crossing in the years before the First World War, they did so on this Welsh coal. The colliery sat next to Quakers Yard station with access in three directions - down the Taff Vale Railway to Cardiff Docks, along the Rhymney Railway, north to Brecon and the Midlands via the Brecon and Merthyr line. Frederick Harris built his own fleet of private owner wagons through the Gloucester Railway Carriage and Wagon Company, hauling his coal cheaper than anyone else. From the pithead in Treharris to a ship's bunker in Liverpool was a matter of hours.

The last pit pony was retired from Deep Navigation in 1973 - not the last in Britain, but a small milestone in a long farewell. The pit kept working through the bitter twelve months of the 1984-85 miners' strike, when photographers came up the Fox Street to document the picket lines outside the colliery gates. It kept working when other valleys' pits closed one by one. It kept working until 1991, when it finally shut after 119 years. The coal washery stayed open another nine months to process a final stockpile of 370,000 tonnes. From 1993 the site was cleared. The slag heaps that had buried the Taff Bargoed for over a century were carted away, and the brick tunnel that had carried the river underground since 1873 was demolished, and the water ran again where it used to.

The combined sites of Deep Navigation, Taff Merthyr and Trelewis Drift collieries became Parc Taff Bargoed, opened for the Millennium. Two new lakes hold what used to be coal yard. Footbridges arch over the river that the colliery once buried. Rugby and football pitches sit where the headgear stood. A commemorative stone at the entrance names the three pits whose ground this used to be. Children come here to feed ducks. There is almost nothing left to see of the work that was done here, the lives that were spent here, the boats that crossed oceans because of what was hauled out of the dark beneath this grass. The colliery is gone. The valley remembers.