Clandon Park was conceived to impress and dazzle. Commissioned by a politician and courtier, Thomas, Lord Onslow, Clandon was designed for entertaining royalty in the countryside. The historic seat of the Onslows, a family who uniquely produced three Speakers of the House of Commons, the house was given to the National Trust by the daughter of the 4th Earl Onslow, Gwendolen, Lady Iveagh, in 1956.

Before the fire, Clandon was one of only five surviving buildings in England by Giacomo Leoni (c. 1686–1746), and was considered to be one of the most complete examples of his work.

The spirit of Leoni’s mentor, the pioneering 16th-century architect Andrea Palladio (1508–1580), presides over Clandon. Leoni’s house has a logical axial plan and an overall classical proportion which are both clearly Palladian in inspiration – although other influences and a certain eclecticism are also at play in the house’s façades.

Leoni marked his arrival in England by publishing the first English translation of Palladio’s I Quattro Libri dell' Architettura (The Four Books of Architecture) between 1716 and 1720. The translation appeared at a pivotal moment in English architecture, acting as a conduit between Palladio and the English aristocracy, and influencing the transition from the Baroque to Palladianism. The latter’s emphasis on clarity, order and symmetry – its harmonic proportions derived from Palladio’s reading of classical architecture – was considered the height of enlightened, sophisticated taste, influencing generations of European architects.

This new style was a sensation, and this communicates in the naming of the Palladio Room, one of the house’s most notable spaces. Indeed, it is possible that this room (datable to 1747 and sadly consumed by the fire) was the first instance of an architect being honoured in this way.

The architectural set piece of Clandon was the entrance, or Marble Hall; a double-height, marble-floored room decorated with outstanding marble overmantels by sculptor John Michael Rysbrack and with the most flamboyant example of a Baroque ceiling in the country. Around this ground floor room was a series of state rooms: a dining parlour, a large drawing room and with-drawing room, a library, a State Bedroom, and a number of smaller, private closets. The first floor contained principal bedroom suites for senior family members, and the second floor for lesser family members and a few personal attendants.

The new house at Clandon marked a pivotal moment for its owners. Leoni’s design was commissioned by Thomas, Lord Onslow (the 2nd Baron) whose father, Richard Onslow, a Whig Member of Parliament, was made a peer in 1716. In the absence of reliable evidence, the Onslows’ decision to replace their extended Jacobean hunting lodge could be interpreted as a response to this elevated status, the design’s noble form complementing the newly-ennobled family.

The house remained in the family for over two centuries, and a number of Onslows made their mark on it: the Speakers’ Parlour, for instance, paid tribute to the family’s parliamentary heritage.

In the late 18th century, renowned landscape designer Lancelot ‘Capability’ Brown was commissioned to remodel the gardens and parkland at Clandon. After a period of neglect, the house was improved and updated by the 4th Earl Onslow towards the end of the 19th century and it was his daughter, Gwendolen, Lady Iveagh, who donated Clandon to the National Trust in 1956.

Immediately after the acquisition, the Trust embarked on a restoration project, reversing many intrusions made in the later 19th century, as well as re-roofing and carrying out large-scale repairs to halt dry and wet rot. The last major restoration work at Clandon was undertaken in the late 1960s by John Fowler, the most experienced decorator of his day.