John Yenn was born in 1750, and was one of the first students to enter the Royal Academy of Arts under the tutelage of Sir William Chambers. Yenn was part of a group of students including James Gandon, Edward Stevens and Thomas Hardwick, whose drawings often featured buildings set in a Picturesque landscape irrespective of whether the subject was a town hall or country house.
As Yenn's reputation grew, Chambers provided him with a number of important positions. In 1780 he become the Clerk of the Works at Richmond Park, followed by similar positions at Kensington Palace, Buckingham House and the Royal Mews in 1782.
In the late 1770s Yenn succeeded Chambers as the 4th Duke of Marlborough's architect at Blenheim Palace. There, he was responsible for creating the Temple of Health in the designed landscape, as well as the new tower of Woodstock Church.
Bibliography
Green, David, Bond, J and H. Maggridge ('After Capability Brown: Blenheim in the later eighteenth century and early nineteenth century' in Blenheim: Landscape for a Palace, eds by J. Bond and G. Tiller (Gloucester: Alan Sutton, 1987), pp. 115-127)
Harris, J 'John Yenn: draughtsman extraordinary', in Catalogue of an exhibition in the Heinz Gallery 3rd September - 19th October 1973 (London: Royal Institute of British architects)