In 1337, a grant of free warren was made to the Belet family for the manor. In 1365 the manor and 13th-century moated house passed into the Restwold family, and it passed through marriage to the Drew family of Seagry, Wiltshire, then the Sambourne family. Margaret Sambourne, the heir to the manor, died in 1494 and an inquisition the following year suggested that she held the manor (then valued at £20) as a trustee on behalf of Hugh Kenepy. Around this time a brick house was built to replace the earlier dwelling. After the death of Sambourne's son, Drew, an inquisition reported in contradiction that the manor was held by the Abbot of Reading; in their work on the Berkshire section of Victoria County History, Peter Ditchfield and William Henry Page write that at this point "the correct tenure had evidently been lost". Through Drew Sambourne's granddaughter, Margaret, the manor passed through marriage to William Windsor, 2nd Baron Windsor. William's grandson, Henry (5th Baron Windsor), sold the manor to Anthony Blagrave by the early 16th century. 16th–19th century The Blagrave family were wealthy landowners around Reading, and the manor passed down through the family (which included mathematician John Blagrave, who built a new house at Southcote); a lease document dated from 1596 suggests that the manor was divided between three Blagrave brothers. Daniel Blagrave, a cousin of John, inherited the manor on the latter's death in 1611. At the time of the English Civil War, during the siege of Reading in 1643, the Blagraves allowed Robert Devereux, 3rd Earl of Essex to use the manor as his headquarters. The Blagrave family, who were sympathetic to the Roundheads, are said to have hosted Oliver Cromwell, John Hampden and Robert Blake for a council of war in one of the house's oak panelled rooms. In January 1649, Daniel was one of the signatories of Charles I's death warrant. In 1665 Elias Ashmole wrote to Mervyn Tuchet, 4th Earl of Castlehaven at "Southcote neere Redding". At some point that century the manor house was largely rebuilt and modernised; the existing 15th century guardhouse and vaulted well were retained. Come the Restoration in 1660 after the end of the war, Daniel fled from England and died in Aix-la-Chapelle in 1668. Southcote saw development with the opening of the Kennet Navigation in the 1720s, where the River Kennet was made navigable by vessels as far