Thomas Onslow, 2nd Baron Onslow

He first entered Parliament in 1702, aged 22 or 23, as the MP for Gatton, Surrey, an underpopulated rural borough that had once had a market in the medieval period.

He was then returned in 1705 to represent the larger settlement of Chichester, West Sussex, followed by Bletchingley (1708–1715) and finally the county seat of Surrey (1715–1717), which then included much of today's Greater London south of the Thames including, for example, Battersea and Lambeth.

The senior branch of the Onslow family continues to own and manage their agricultural business and the Clandon Park parkland to this day.

However, in the 18th and 19th centuries the family owned several thousand acres of farmland scattered across many villages in Surrey from which they derived an income.

[4] According to research carried out under University College London's Legacies of British Slave-ownership project, Clandon House was built by Onslow possibly as a result of his wife's slavery-derived fortune.

Thomas Onslow, 2nd Earl of Onslow
Clandon Park House was transformed from a large manor house to a lavish English country house by this Lord Onslow, but the 3rd Lord Onslow had its interiors finished. It features a two-storey Marble Hall and marble chimney and other pieces by the Flemish sculptor Michael Rysbrack , but the interior was gutted by fire in 2015.