Basildon Park was designed by John Carr of York and is one of his masterpieces. A golden Palladian mansion, it was built by Sir Francis Sykes of Ackworth Park, Yorkshire (1730–1804), 1st Bt, a nabob who had made a fortune as Resident at the Court of the Nawab of Bengal. It was sold in 1838 to the wealthy draper James Morrison (1789–1857), MP. In partnership with the dealer William Buchanan, Morrison put together one of the most distinguished painting collections in Britain in the second quarter of the nineteenth century, although most of it has, unfortunately, since been dispersed.

The newspaper proprietor Edward Iliffe (1877–1960), 1st Lord Iliffe, purchased the Basildon Park in 1928 with the intention of annexing his own estate at Yattendon. Having little interest in the mansion, it was quickly sold, with a much smaller parcel of land, in 1929 to George Ferdinando who, at one point, hoped to export the whole house to America but the Depression intervened and only some parts were dismantled. Basildon was subsequently purchased and restored by 1st Lord Iliffe's son, Edward Langton Iliffe (1908–1996), 2nd Lord Iliffe, and his wife, Renée Merandon du Plessis (1916–2007), Lady Iliffe. They had bought it back in 1952 and later donated it and many of their Baroque and Rococo pictures, bought at Agnew’s and Colnaghi’s, to the National Trust in 1978. More recently, two small capriccio landscapes by Giuseppe Zais, a portrait by Batoni, and a major work by Madame Vallayer-Coster were acquired in lieu of tax in 2010.