Built originally by Sir Ralph Coningsby, the house remained with the family until 1658 when it was sold to Sir Nicholas Hyde whose grand-daughter Bridget married the eldest son of Earl Danby who was later created Duke of Leeds. In 1685, Bridget suceeded to the estate and a few years later her huband became the second Duke of Leeds. The house remained with this family until the sixth Duke of Leeds sold it ( in 1799) to Henry Browne who was there until 1823 when a succession of owners followed ending with 'Glaxo' in 1992.
(Information from www.brookmans.com and BritishListed Buildings.co)
It may be assumed that the drawings dated 1795 were made for the sixth Duke of Leeds and the later copies dated 1807 and 1808 ,, were presumably made as Soane office record drawings.
P. Dean, Sir John Soane and the country estate, 1999, p.187 has the following account. 'Soane designed numerous outbuildings, including a peachery, dairy, lodge, icehouse and glasshouse, as well as repairs to the existing Elizabethan house, which was redecorated by John Crace (BBA/115-127). The work came to a total of £3,355 3s 8d (L/C/383). The house, which survives was restored by Sir Ernest George c.1893-4 (see Pevsner, Building of England: Hertfordshire, p. 263) when the garden buildings were also reconstructed 'in a style to match the house (see SM archive, letter to DS [Dorothy Stroud] 4 August 1954).
Sir John Soane's collection includes some 30,000 architectural, design and topographical drawings which is a very important resource for scholars worldwide. His was the first architect’s collection to attempt to preserve the best in design for the architectural profession in the future, and it did so by assembling as exemplars surviving drawings by great Renaissance masters and by the leading architects in Britain in the 17th and 18th centuries and his near contemporaries such as Sir William Chambers, Robert Adam and George Dance the Younger. These drawings sit side by side with 9,000 drawings in Soane’s own hand or those of the pupils in his office, covering his early work as a student, his time in Italy and the drawings produced in the course of his architectural practice from 1780 until the 1830s.
Browse (via the vertical menu to the left) and search results for Drawings include a mixture of Concise catalogue records – drawn from an outline list of the collection – and fuller records where drawings have been catalogued in more detail (an ongoing process).
Contents of North Mymms Park, Hertfordshire: survey plan of house, designs for lodge house and peachery, 1795 & 1807 (7)
-  Survey plan of ground floor
-  Record survey plan of ground floor to a lesser scale than drawing 
-  Design for a lodge
-  Design for a lodge as  with section
-  Record drawing of design for a lodge (as [3-4]
-  Record drawing of design for a lodge as [4 verso]
-  Design for a peachery