The first designs for the Castello d’Aqua – otherwise known as the Water House – appear to have been made in late summer 1792. The entry for September 15th of that year in Soane’s Journal reads: ‘Sent per post to Provis a drawing of Water House at Wimpole on a sheet of Copy Paper’.

In January 1793, T. & J. Taylor of High Holborn made aquatints of a perspective and of a plan and section of the Water House, to be published as plates XLI and XLIII of Soane’s Sketches in Architecture containing Plans and elevations of Cottages Villas and other useful buildings. Soane’s introduction to the book is dated March 1793. The description of the perspective is as follows: ‘Design for the Castello d’Acqua, now building at Wimpole in Cambridgeshire, a seat belonging to the Earl of Hardwicke. Its exterior representation is that of a mausoleum. The snakes are cut in the solid, and do not project, as shewn by mistake in this view’.

A similar design appears on an undated drawing (8/4/9). Both differ from the model in that the niches do not start at ground level and hold a shelf with an urn on it. The lowest level of the drum is decorated with ‘S’ fluting. Their sections, however, show a shallow basin within the building, like that seen when the model is open.

Soane’s assertion that the Water House was ‘now building’ in early 1793 was probably mild exaggeration, for further drawings were sent to Provis on July 26th (Journal, Earl of Hardwicke, 1793 July 26). The original of this drawing is in the Museum (8/4/10) and it shows a design closer to that of the model in the treatment of niches, panels and drums. The construction of the interior has been altered, the shallow basin being replaced by a flat bottom, with a vault beneath to spread the weight of the water lying on it.

These details could suggest a date for the model somewhere between January and July 1793, but it is a little strange – if this is the case – that it is not mentioned in any of the accounts when other models are.

The other models include one for the Drawing Room at Wimpole made by the joiner Thomas Shephard (Wimpole 1791-1794, p 43) and delivered to Henry Provis, the Clerk of Works, on August 20th 1791 (Journal, work undertaken for the Earl of Hardwicke, entry of same date). Another was ‘a model for the handle to the Shutters of Anti Liby’ (Journal, work undertaken for the Earl of Hardwicke, 1793 Dec. 17th). Neither of these survives. It should not be forgotten that Henry Provis was a model-maker – we know he made several models for the Bank of England, among them the Rotunda – and he could, therefore, have built the model of the Castello d’Acqua.

As regards the construction of the Water House, there is a bill for extra foundations for the building dated October 26th 1793 (Wimpole 1791-1794, p 52).The charge for the ‘Centering to Dome of Water House including the Struts, Braces & Curbs and lathing on d_ to receive composition arch’ was made between September 1792 and November 1793 (ibid p 23). On December 21st 1793 Provis noted the Cost of the ‘Carr. Of brass pipes for Water House’ (Earl of Hardwicke/Wimpole/ H. Provis’s disbursements…’.

David Adshead, "'Like a roman sepulchre', John Soane's design for a Castello d'acqua at Wimpole, Cambridgeshire, and its Italian origins" in Apollo, 1 April 2003, pp. 15-21, fig. 7.