From 1790 to 1795, Soane made alterations to Wimpole Hall and built various estate buildings, costing a total of £17,863 17s 5d. Further alterations to the first floor were made in 1800.

Soane met Philip Yorke, later Lord Hardwicke (1757–1834), on 28 January 1779, among the Greek ruins of Paestum while both men were visiting as Grand Tourists. Soon after returning to England, Yorke commissioned Soane for alterations to his residence at Hamels Park, Hertfordshire (q.v.). When Yorke inherited the earldom from his uncle ten years later, he immediately called on Soane for building work at his new residence, Wimpole Hall. Wimpole is the result of a series of building phases, including a core built in the mid-17th century, additions by James Gibbs in 1719, and alterations by Henry Flitcroft in the 1740s. As Ptolemy Dean points out, 'Wimpole had developed over many generations, yet no single phase of construction had ever entirely eradicated the work of its predecessors, something that would prove to be an important consideration in the development of Soane's scheme' (P. Dean, p. 67). The gardens too had developed with marks left by past owners and Lord Hardwicke commissioned Soane for not only alterations to the house but for buildings on the estate, to be set within an improved landscape devised by William Emes (1729/30-1803).

Soane records first visiting Wimpole Hall on 10 June 1790, less than a month after Lord Hardwicke succeeded his uncle, the second earl. Soane took plans with 'Guibert', probably a local clerk, and on 25 June he called on Lord Hardwicke to discuss plans for the house. Another journey to Wimpole was made in August. On 3 January 1791 Soane sent in the post designs for a new drawing room and a model of the room was delivered ten days later. The drawing room replaced an existing ante-room, secondary staircase and subsidiary space, and a new secondary stairwell was built in the neighbouring east courtyard, together with water closets. The drawing room, later referred to as the Yellow Drawing Room, consisted of a north-facing barrel-vaulted space leading to a spacious top-lit interior set deeper within the house, its lantern raised on round arches springing from four piers. The new room rose up through two storeys, heavily disrupting the first floor's circulation and essentially dividing the storey. Soane attempted to alleviate these issues with new corridors and staircases. He also inserted a series of top-lighting. A new secondary stairwell in the east court blocked up some window, thus necessitating top-lighting over the principal staircase. At the same time, Soane made additions to the library ante-room at the opposite end of the house, adding two round-arched western bays to Gibbs's original (though the drawings in the Soane museum show only one added bay). Although not sufficiently represented in the Museum's drawings collection, it is evident that Soane built the house's Plunge Bath and he made minor improvements throughout the house.

Set within the estate and surrounded by William Emes's new plantings, Soane built a hothouse, water reservoir, three cottages, an entrance screen, a farm yard and a hen house. An intended dairy for Lady Hardwicke was not executed. Soane experimented with a variety of architectural styles in his Wimpole estate buildings. His dairy and cottage designs exemplify the architect's primitive style, a theme that had earlier been employed at Hamels Park in 1787. Soane had designed in this style for other clients, including a dairy for Lady Craven in 1781 (unexecuted, q.v.), a dairy at Lees Court (not as executed, q.v.). As John Martin Robinson describes, Soane's primitive entails: 'thatched roofs, wide overhanging eaves, and Doric porticoes, the baseless columns of which were made out of the trunks of elm trees with the bark left on' (J.M. Robinson, p. 46). Soane's primitive aesthetic is probably influenced by Robert Adam's 'Castle Style', which was a synthesis of the Scottish vernacular and Roman motifs (ibid, p.46), as well as Marc-Antoine Laugier's Essai sur l'architecture, an essay that pronounced the foundations of classical architecture as derived from an ancient rudimentary hut of tree trunk columns and utilitarian roofing. At Wimpole, Soane employed the primitive to varying degrees, combining its elements with more recognizably neo-classical motifs, such as domed roofs, pediments, and triumphal arch forms. The barn at Wimpole is a unique departure for the architect, its washboarded and thatched exterior revealing an interest in the local vernacular and even, as suggested by Ptolemy Dean, a 'sophisticated pattern of structural timber framing modelled on Swiss precedent' (P. Dean, p.70). Further exemplifying Soane's breadth is the water reservoir, later referred to in his Sketches in Architecture (1793) as a 'Castello d'acqua', which resembles a Roman sepulchre chamber and is based on a design Soane made as a Grand Tourist in 1779.

Soane enjoyed 35 years of patronage by Lord Hardwicke and his extended family, including building works at Hamels Park, Hertfordshire, and Sydney Lodge, Hampshire. Today, Wimpole is owned by the National Trust and Soane's building works are mostly preserved, though some estate buildings have been demolished or have deteriorated since their construction.

Drawings of Wimpole Hall are available in other collections and are catalogued in David Adshead's catalogue for the National Trust, Wimpole: architectural drawings and topographical views, 2007. For further drawings of the drawing room and first floor alterations, see the National Trust collection. For more variant designs of the cottages, see Vassar College Art Gallery and Canadian Centre for Architecture (CCA). Additional drawings for the dairy are available at the Victoria and Albert Museum. The CCA possesses one drawing for the entrance screen, and two are in the V&A collection. A model of the 'Castello d'Acqua' is at the Soane Museum (1148 M).

Literature: J. Wilton-Ely, 'The Architectural Models of Sir John Soane: A Catalogue', Architectural History, Vol. 12 (1969), p. 13; D. Stroud, 'The charms of natural landscape: the park and gardens at Wimpole II', Country Life, 13 September 1979, pp. 758-762; J.M. Robinson, Georgian Model Farms, 1983, 45-46; D. Stroud, Sir John Soane, architect, 1984, pp. 146-9; P. du Prey, Sir John Soane, 1985, in series of 'Catalogues of architectural drawings in the Victoria and Albert Museum', 1975, cat. 140-1; M. Richardson & M. Stevens (eds), John Soane architect: master of space and light, 1999, pp. 122-126; P. Dean, Sir John Soane and the country estate, 2006, pp. 65-77; D. Adshead, Wimpole: architectural drawings and topographical views, National Trust, 2007, pp. 69-99.

Christopher Woodward's typescript catalogue of some Wimpole drawings, c.2000, has been instrumental to the creation of this catalogue.

Madeleine Helmer, 2012