Previous owners
Until the nineteenth century the manor of Kingswood was merely about 2000 acres (about three sq. miles or eight sq. km) of woodland and agricultural land in the parish of Ewell. In the Middle Ages it was held by Merton Priory. When the Priory was dissolved in 1538, it reverted to the Crown. Queen Elizabeth granted it in 1563 to the Howards of Effingham, who also owned Reigate Priory. Charles, Lord Howard of Effingham, later Earl of Nottingham, was Lord High Admiral of England and led the English fleet against the Spanish Armada. The Howard line died out in the seventeenth century, and the manor was owned by various families until it was bought by Thomas Alcock in 1835.

Alcock bought the manor with the object of building, and his house was completed in 1837. He had been M.P. for Newton in Lancashire 1826-1830 and contested Ludlow in 1837 and 1839. He was M.P. for East Surrey from 1847 to 1865. In addition to Kingswood Warren, Alcock was responsible for the building of nearby St Andrew’s church. It is an exact copy of the mediaeval church at Shottesbrooke in Berkshire, where Alcock had spent some time as a guest of the Vansittart family. Thomas Alcock died at Malvern in 1866 and is buried in St Andrew’s churchyard.

Thomas Alcock’s nephew, Thomas St Leger Alcock, sold Kingswood Warren in 1873 to Sir John Cradock Hartopp. Sir John’s main aim in buying the estate seems to have been to use his rights as Lord of the Manor to enclose the commons and exploit the land for his own profit. Some of the commoners agreed to sell their rights to him, but others resisted and in 1877 a lawsuit was started against Sir John to restrain him from enclosing. In 1884, Sir John’s solicitors became insolvent and absconded; Sir John was involved in their ruin and became bankrupt. However, Sir John had mortgaged his rights to the commons, and the mortgagees continued to defend the lawsuit through various courts until final judgement was given against them in 1889, nearly thirteen years after the action was started. The commons were finally regulated by an Act of Parliament after another long legal battle with the mortgagees before Select Committees.

In 1885 Sir John Cradock Hartopp sold the estate to Henry Cosmo Orme Bonsor, the son of Joseph Bonsor of Polesden Lacey. He was a City financier, a partner in the brewery of Combe & Co, and a Director of the Bank of England. In 1898 he organised an amalgamation to form Watney, Combe & Reid, of which he remained chairman until 1928. In 1897 he turned his attention to railways and became chairman of the South Eastern Railway; in the same year, the line was extended from Purley to Kingswood. In 1899 he organised an amalgamation with the London Chatham & Dover Railway, and became chairman of the managing committee. In the same year he formed a private syndicate to extend the line from Kingswood to Tattenham Corner to catch the racegoing traffic; the extension was a great success and was later taken over by the South Eastern Railway.

Cosmo Bonsor was also a public benefactor, reorganising the finances of Guys Hospital and sitting as an unpaid Commissioner of Income tax. In strong contrast to Sir John Cradock Hartopp, he was loved locally for his kindness and generosity to all. He was created a baronet in 1925 and died four years later in Nice; he is buried in St Andrew’s churchyard.

The rising cost of maintenance and entertainment caused Mr Bonsor to put the estate on the market in 1906. It failed to sell then, but was finally broken up and sold in a number of separate lots in 1912. The mansion plus 102 acres of land was bought by Joseph Rank, the founder of the milling empire. Rank sold the property in 1928 to an American, Clinton D. Winant. Winant was connected with the oil industry and was the brother of John Winant who was US Ambassador to the UK during the second world war. Two years later the house was on the market again because Winant had become insolvent, but it was not sold until 1932 when it was bought by the Walton Heath Land Development Company and subsequently conveyed to Richard Costain.

In 1933 Kingswood Warren and a small area of land were sold to Mlle Rossignon, who transferred to it from Switzerland her girls’ finishing school. This did not last long and Mlle Rossignon turned Kingswood Warren into a hotel for 32 guests. The outbreak of war in 1939 terminated what had never been a very successful venture; the hotel was closed in 1940 and Mlle Rossignon died soon afterwards.

In 1940 Kingswood Warren and St Monica’s on the other side of the railway were bought by the Legal & General Assurance Society Ltd as offices and residences for staff evacuated from London. In 1947 L&G transferred all their activities to St Monica’s and Kingswood Warren was again on the market. In early 1948, it was bought by the BBC to house its Research Department, which had expanded considerably during the war and which was based partly at Bagley Croft near Oxford and partly at Balham.