A pen and ink and watercolour design for a grotto or a tunnel, with a wooden fence above.

Thomas Sandby was employed by William Augustus, Duke of Cumberland from 1746, first as Draughtsman, and from 1764 as Steward of Windsor Great Park, where the Duke had been appointed Ranger in July 1746. Sandby in effect acted as Deputy Ranger to both William Augustus and his nephew (and successor as Ranger), the King’s brother Prince Henry, Duke of Cumberland. He was resident in the Great Park for much of his adult life.   

Sandby also worked as an architect. In the list of subscribers to Chambers’s Treatise of 1759 he was described as Architect to the Duke of Cumberland and he designed an extension to the Duke’s Windsor home, Cumberland Lodge, at around the same time. In December 1768 Sandby was appointed first Professor of Architecture at the newly founded Royal Academy and from 1770 he delivered a series of six lectures at the Royal Academy, which were repeated annually until his death. In 1777 he was appointed Architect of the King’s Works, with James Adam (brother of Robert), and from 1780 to 1782 he was a member of the Board of Works as Master Carpenter, a titular office. His work in St George’s Chapel in the 1780s and his design for a picture gallery at the west end of the North Terrace were probably associated with these appointments.   

This drawing belongs to a group of designs by Sandby in the Royal Collection relating to various works carried out in Windsor Great Park. The architect for the creation of Virginia Water in 1750 by the Duke of Cumberland was Henry Flitcroft rather than Thomas Sandby, and this drawing is related instead to Sandby's extensive works at Virginia Water in the 1780s. There was extensive flooding in 1768 and 1782, and Sandby was responsible for the enlargement of the lake and a new cascade and grotto. There is a large number of drawings of rockworks relating to this period in the Royal Collection, with further groups at the V&A, Bodleian Library, and the Sir John Soane's Museum.