The Thornton family coat of arms

South Mills was included in the Manor listed under Chalton in the Domesday Book of 1086. The medieval manor including Chalton, however, was known as the Manor of South Mills or Holwell's

The Victoria County History, published in 1910 included brief histories of all the manors in the county. Part of Adeliza's manor noted in Domesday Book probably later became the Manor of Mogerhanger. Another part became the Manor of South Mills alias Holwells. At sometime after the Domesday Book the Honour of Leicester became overlord of the manor. An honour was a group of manors which were designed to support a lordship.

The first known tenant of the manor was William Lovel who held half the manor in the early 13th century. He was succeeded by a family named Harcourt, first recorded in 1270 when Henry de Harcourt and Cecilia, his wife, conveyed land and a share in the mill to Richard de Harcourt.

The manor appears to have been alienated by the Harcourt family at some time between 1319 and 1346 when it was held by Robert de Holwell, John Malyns, Nicholas Crowe and John de la Hay. In 1428 three people named as holding the manor were Thomas Malyns, Gerard Crowe and Joan Hende but the Holwells seem to have had the chief interest as Richard Holwell conveyed the manor to John Fitz in 1433.

By 1469 the manor was in the hands of George Gascoigne, who then alienated it to John Maningham who retained it until 1484 then transferred it to John Mordaunt and John Vynter, perhaps as trustees. In 1549 John Aleyn alienated the manor to Humphrey Browne and others, again, perhaps, as trustees. The manor is next mentioned in surviving records in 1679 when it was in the hands of Thomas Cheyne, who conveyed it to Thomas Bromsall, later passing to the Astell and Thornton families, the latter holding the manor from 1777 until 1864 when William Thornton died without issue. The manor then passed to the Dawkins family which held it into the 20th century. A succession of Law of Property Acts in the 1920s abolished copyhold tenure, manorial fines and, effectively, manors themselves in all but name.