Old Cromwell House stood on a site presently occupied by the Stag Brewery and faced onto what is now Williams Lane. The stone and ironwork gates still exist in Williams Lane although they have been moved from their original site some 40 meters to the west. Old Cromwell House was a two-winged, brick-built mansion with high surrounding walls whose land stretched north from the Lower Richmond Road to the tow path on what is now Thames Bank.
It is likely that the house is named after Thomas Cromwell who was granted the Manor of Mortlake by Henry VIII in 1536. His sister Catherine may well have lived in the house with her brewer husband, Morgan Williams.
The old house also had connections with Oliver Cromwell although there is no evidence that he owned it. Many of his supporters lived in Mortlake and the two John Blackwells (father and son) who became captains in Cromwell’s army, lived in Cromwell House from 1624 until 1660 when the house was forfeited to the Crown. There is a reference to a dark hole in one of the gable ends, known as "Old Noll’s Hole" which was to have afforded Oliver Cromwell temporary accommodation if he was in the house and his life was in danger. Old Noll was a nickname for Oliver Cromwell.
Edward Colston, an early slave trader, lived in the house from 1695 until his death in 1721. He was an enthusiastic gardener and the grounds of Cromwell House were reported to be most impressive. A gazebo was built into the north wall which gave good views onto the river. The Aynscombe family then lived in the house for almost 60 years, the last surviving member, Valentina dying there in 1841.
Old Cromwell House then fell into disrepair. James Wigan, a partner in the Phillips and Wigan brewery, which was then situated on the old Mortlake manor house site, acquired the lease of the old Cromwell House, had it demolished in 1857 and built a new Cromwell House. Robert Philip Pope was the architect and the house stood at the river end of the estate with its large gardens facing onto Williams Lane. Wigan’s Cromwell House was an impressive red brick Victorian villa with fine Tudor style chimneys. It had 14 bedrooms, a nursery and school-room, servants’ quarters, vast cellars, a billiard room and several offices and other minor rooms. The estate consisted of five acres of land, the house, barns, stables, yards, a landscaped garden, orchard, outhouses and edifices, and it was enclosed by brick walls.
James Wigan and his young wife Maria moved into their new house in June 1858. Maria went on to have 13 children, all of whom were born in the house. James became a wealthy man and active in both local political and church matters. He died in 1902. Maria died in 1918, having lived in the house for 60 years.
Cromwell House became derelict but a caretaker lived in part of the property for some 20 years. The house survived the war but only to be demolished in 1947 when the land was bought by Watney's. The brewery developed most of the site with the exception of about two acres on which the house had stood and which faced the river. The brewery built a third Cromwell House on this site. Employees of the brewery lived in the modern terrace of houses until that too was demolished in 1990. This piece of land near to the river was sold and the present Parliament Mews was built in 1992. The original high boundary walls of Cromwell House still exist today as the boundary wall of Parliament Mews.