This was not the first scheme designed by Soane in a Castle style. The domestic offices at Skelton Castle (1790-1) had embattled walls and his alternative designs for Dunninald House included two sets of designs in a Castle style (q.q.v). More successful were the embattled stables at Port Eliot, 1804.
Of 'the old Tortworth Court ... All that survives is a ruined fragment'. (D.Verey and A. Brooks, Gloucestershire 2: the Vale and Forest of Dean, 2002, pp.772-3. The new Tortworth Court was built 1849-53 by S.S.Teulon (1812-73) who also designed the SW lodge.
There are in the Soane Museum's green box files under Tortworth two (indistinct) photo copies of photographs (Conway L12/20(19) and L12/20/(18) of two designs for a gate house. These were sold at Christies, 30 November 1983, lot no.81. One (18) is the same as drawing , the other has alternative designs of which the right hand one also relates to drawing  while the left hand design is the same as drawing .
For a note on another drawing sold at the same sale see drawing  for Soane's design for a prospect tower for Lord Ducie
A design for a 'Prospect House', c.1796 in in the Victoria & Albert Museum see P.du Prey, Sir John Soane, 1985, in series of 'Catalogues of architectural drawings in the Victoria and Albert Museum', catalogue 118, pp.57-58
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.
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Contents of Tortworth Court (Gloucestershire): unexecuted designs for a pair of gate lodges in a Castle style for Lord Ducie and design for a prospect tower 1796 (12)
-  Designs '1' to '4' for a two-storey lodge
-  Design '3' to a larger scale
-  Design for a two and a half-storey lodge
-  Slightly variant design to drawing 
-  Perspective of the back relating to drawings  and 
-  Alternative design for a two and a half-storey lodge
-  Variant design to drawing 
-  Back elevation to drawing  with plan
-  ' Design No 1' for a two and a half-storey lodge
-  ' Design No 2', variant to drawing 
-  Design for a two and a half-storey lodge on a rectangular plan
-  Design for a prospect tower