The date at which work on the Dark Hill gale began is unknown but in May 1813 an agreement was entered into between Stephen Blanch and William Jordan to sell the colliery to a John Hawkins for the sum of £170 subject to supplying 8,000 tons of coal to Glover & Kippersley of Gloucester.  This transaction was obviously carried out as in the same month came an indenture between Hawkins and David Mushet.
The 1841 Awards confirmed the gale as being awarded to David Mushet although it would appear that no work was done on the gale until 1845 when an output of 164 tons is given against the gale.  The following year this had increased to 1,977 tons. By 1847 it would appear that Mushet had obtained the neighbouring Shutcastle gale. (Galed on the 27th June 1842 to a George Gwilliam, although there is a mention of a Shute Castle being worked in 1725.) Following David Mushets death on the 7th June 1847 the two gales, together with his famous Dark Hill Iron Furnace, were for sale by auction on the 13th July. The sale notice described the properties as;-
‘adjoining each other, situate in the said township of West Dean, with the buildings, coke-yards, tram plates, and other matters and things used in working the same collieries, and now being in, upon, or under the same.
The Collieries comprise the coal under about 100 acres of land, and are estimated to contain 6,000 tons per acre of the Coleford High Delf Coal in a vien of 6 feet thickness.
The mouth of the Dark Hill Level lies within 50 yards of the Severn & Wye Railway, and within about 300 yards of the Furnace.
THE DARK HILL COLLIERY is subject to a yearly rent or Royalty of three half-pence for every ton of Coal brought out, payable to the Crown half yearly, and if such rent shall not amount within any year to £3 then a rent of £3 in lieu thereof.
THE SHUTCASTLE COLLIERY is subject to a yearly rent or Royalty of one penny for every ton of Coal brought out, also payable to the Crown half-yearly, and if such rent shall not amount within any year to £2, then a rent of £2 in lieu thereof.’
It would appear that the sale did not go through and under the terms of David Mushets will the furnace and the two levels were left in equal parts to his three sons, David, William and Robert. Due to family disputes David and Robert also held Williams share and in September the partnership between David and Robert was dissolved. The ironworks and the collieries were now held by David alone and it would appear that around this period a Mr. Goodrich Langham came to have an interest.
In November 1874 ‘Best Coleford High Delf House Coal’ at 14s per ton was being advertised as being available from the Darkhill Colliery but who was selling it is unfortunately not given. ‘Steam and Lime Coal’ was always on hand.
In 1875 the Coleford Coal Co. were undoubtably working the Dark Hill Colliery although this cannot be confirmed. The evidence is taken from the fact that the loading point built for the company was adjacent to the Dark Hill level.  It is possible that Langham, together with William Henry Fryer (who had held an interest in Shut Castle from an earlier date), the Revd. Croft Worgan Dew, and Edward Livesay Waddington were the proprietors of the Coleford Coal Co., although as yet this has not been confirmed.
The next reference to Dark Hill Colliery comes in 1877 when it was stated that Richard Thomas had taken a lease on the gale for a period of 15 years from the 24th July. The gale was conveyed from Waddington, Langham, Fryer and Dew to Thomas on the 8th January 1878.  However, it appears that he soon ceased work as in October 1888 it was reported that the Dark Hill Colliery had not been worked for 5 years and as such was liable for forfeiture. Thomas obviously extended the time for working, even if no work were being done. It is possible that parts of the gale were sublet as in 1894 the output from Dark Hill is split into three parts.  A Mr. Cook was producing 583 tons, a Mr. Sims was producing 432 tons and a Mr. Hoare, 268 tons.
In November 1899 2/6ths of the gale was conveyed to Mr. Thomas Bennett Brain by a Daniel Jennings for the sum of £10. In December he acquired a further 1/6th from E. M. Langham, Diana Langham and Lucy Langham whilst the following year, 1900, saw him acquire the rest of the gale in September.  1/6th came from Sarah Todhunter and Isabella Todhunter, who had gained their interest from Croft Worgan Dew by 1892, and the remaining 2/3 came from the Langhams. He also acquired a part share in the Shut Castle gale mainly in parallel arrangements.
An advert appeared in November 1900 in the Dean Forest Guardian advising that ‘Good Household Coals’ could be obtained from the Dark Hill Colliery at a price of 17/6 per ton. Brain, however, did not remain working Dark Hill for long as in 1907 he leased it to Thomas Pegler.  A further lease appears to have taken place, either on the whole or part of the property, as Potts Mining Register  for 1908 gives Nash Bros. as working the gale employing five below and three above ground.  In 1914 the ownership of the gale was conveyed by Ellen Scudamore, as executor of T.B. Brain’s will (Brain had died in September 1909 and appointed his daughters Emily Goold and Ellen Scudamore as his executors), to a Miss Mary Ellen Goold, who, at the same time, also recieved the 1/6 share in Shut Castle.
It is doubtful that after the death of Brain that any work was done at Dark Hill, at least from the Dark Hill Level, as in January 1915 a building on the site was reported as being delapidated and in June 1918 it was stated that the land and buildings had not been occupied for at least 12 years. If this was the case then Peglar was probably working the Dark Hill gale from another of his interests, possibly Elsmores No 2 gale.
Indeed Dark Hill gale was being worked from several adjoining gales. In March 1895 James and Martin Nash, as lesees of the Dark Hill Endeavour gale, wished to drive a water-level so as to drain and work the remaining coal in Dark Hill. The following year the Revd. A.W. Latham of Lydbrook was applying to work another seam of coal in the Dark Hill gale. Latham had formed the Darkhill & Ellwood Colliery Co. whose railway wagons certainly worked out of the Fetterhill Sidings. Latham had also by 1899 gained the 5/6 share of Shut Castle and was undoubtably working this as part of Darkhill & Ellwood. He also held interests in several adjoining gales including Hopewell Engine.
Latham died in May 1915 and his interest in Shut Castle passed to ‘Lloyd and others’ whilst in 1918 the 1/6 share  passed to Messrs. Perkins and Pardow. In 1926 ‘Lloyd and others’ conveyed their interest to Peglar who in turn transferred it in 1935 to T.S. Thomas via M. Hoare. Thomas had also managed to acquire the 1/6 share  by 1936. By 1941 Darkhill was also in his hands but it is unknown if much work was done. In 1954 Darkhill was in the hands of B. Ellis and W.J. Brown whilst Shut Castle was with the Manor House Collieries Ltd.