The Duke of Portland's document collection, held at Nottingham University, reveals that in 1837 the 4th Duke was to concede to his mill leasees and other water-powered mill owners on the River Maun in Mansfield, that a large regulated head of water was required to ensure continuity of supply all year round to avoid disruption to the businesses. In order to make the project viable, the Duke had to flood 72 acres of his farmland including land he was obliged to acquire from the Unwin family. The relevant minutes of the meeting are copied below:

Forms part of the Portland archival bundle Pl E12/6/19/173. Nottingham University

First Party: The Most Noble William Henry Cavendish Scott, Duke of Portland.

Second Party: Dickinson Ellis; Charles Stanton; Mark Porter; William Adlington; F. and T. Wakefield; Richard Girdler; Leavers and Greenhalgh; and Richard Hardwick (owners and occupiers of mills on the River Maun)

Agreement by (1) to construct and keep repaired a reservoir or dam of 72 acres on land belonging to him near King's Mill in the parish of Sutton in Ashfield in Nottinghamshire.

Agreement that during construction work water shall be sent down during the daytime. The Duke is allowed to use water from the natural stream to irrigate his lands near the river on six Sundays in one year as long as this does not disturb the mill owners. Agreement that Messrs Wakefield should supervise the regulation of the water.

Agreement that for 20 years after 25 Mar. 1839 annual rates are to be paid by each mill owner or occupier to the Duke (as specified in a schedule), and that after 20 years lower rates are to be paid (as specified in a second schedule).

Any disputes relating to the agreement are to be decided by two arbitrators chosen by the Duke and by the disaffected party, and by an umpire chosen by the arbitrators.

The story of water-powered mills on Mansfield's River Maun begins in 1771 when the Lancastrian industrial pioneer, Richard Arkwright, introduced what became known as the 'water-frame' at Cromford, Derbyshire. This was a water-wheel powered spinning frame that subsequently revolutionised the textile industry through its giant leap in improved efficiency. By 1800 Mansfield had around 700 knitting frames operating in a very inefficient cottage industry employing orphans & children from destitute families. As competition from the mechanised mills became fierce, prices tumbled and poverty and unemployment rose. The landowner, Nottinghamshire born, William Cavendish-Bentinck, the 3rd Duke of Portland, a member of the aristocratic Whig party but later Home Secretary from 1794-1801 in William Pitts' Tory government, commissioned the development of water-powered spinning mills along the River Maun in order to compete in the market and reduce mounting unemployment & poverty.

The first of the Duke's new mills was Hermitage Mill, built 1782, currently occupied by a builder's merchant accessed on Hermitage Lane. Little Matlock Mill next c.1785 and is still standing in a relative good state on the corner of Sheepbrige Lane and the new industrial road/Quarry Lane crossroads. Then Field Mill, on Nottingham Road, leased in 1788 - demolished 1925. In 1795, the Duke also financed the conversion to cotton spinning of the Old Town Mill built circa 1744 as a corn and malt mill. Also built 1795 was Stanton's mill and is still occupied. The last textile mill was Bath Mill built in 1792 but now derelict.