The wealth of the Leech family was derived from land and properties in Long Millgate and Ancoats, which they acquired in the seventeenth century. Increasing industrialisation in the late eighteenth century brought more intensive development, and these properties increased in value.
The Ancoats land, known as Brownsfield, was situated on the south-west of Ancoats Lane (now Great Ancoats Street). In the 1790s a new canal was proposed between Sowerby Bridge and the Bridgewater Canal, intersecting the Leech land. The newly formed Rochdale Canal Company offered to build a bridge over the canal, drain the land, cut the canal no wider than necessary and give the Leech family other advantages, notably permission to build coal wharves.
In 1824, Thomas and John Leech went into partnership with the Gerrard family to build a cotton mill and warehouse on the Brownsfield land.
Brownsfield Mill is built of heavy, timber-floored construction, and comprises two multi-storeyed wings built to an L-shaped plan. Until the late nineteenth century it was apparently occupied only by one or two tenants at any time, mostly firms involved in the cotton-spinning trade. By the end of the century, however, the mill was occupied by a number of small firms in a wide variety of trades.
The income derived from the ownership of the mill supported all members of the Leech family, but in the 1870s the family lost overall control of the property when one of Thomas Leech’s children sold her share to Rylands and Spencer. In time this share was taken over by Pall Mall Properties Ltd, and in 1929 Brownsfield Estates Ltd was formed and the mill was sublet. Eventually it was sold in 1984, ending the Leech family’s connection with the property.
Brownsfield Mill has at least three claims to fame. Firstly, it is one of a handful of surviving mills in the Ancoats area, one of the cradles of the Industrial Revolution and now a nominated World Heritage Site. Brownsfield and its close neighbours Sedgwick Mill, Beehive Mill and Murray’s Mills illustrate the chronological development of cotton mill architecture from 1800 to the 1920s, and form part of the Ancoats Conservation Area.
Secondly, it was in Brownsfield in 1910 that Sir Alliott Verdon-Roe established A.V. Roe & Company, one of the world's first aircraft manufacturers. Ernest Bosdin Leech remembered: 'When I looked round the mill after my father’s death in 1912, I was astonished to find in one of the lower storeys a fitted-up aeroplane. It was the first I ever saw in England. I had only seen them in Germany in Berlin. Avro (A.V. Roe) was then a tenant building there his earlier machinery. The firm of Everard to which he was attached made the well-known Bull’s Eye braces on the premises and these I have worn for many years to stimulate home industry'.
Thirdly, the rent collector and clerical assistant employed by the mill's part owners Pall Mall Properties was none other than the artist L. S. Lowry, who worked at Brownsfield from 1912 until his retirement in 1952, and whose handwriting can be seen in several of the minute and account books.