The Devon Gardens Trust has been instrumental in campaigning for the integrity of the grounds and gardens at Knowle.
The Knowle gardens are on the Devon Local Register:
Devon Local Register | Devon Gardens Trust
This is from its casework pages, including a link to the DGT's letter of objection to the planning application:
Casework | Devon Gardens Trust
See also: www.eastdevon.gov.uk/1652-devongardenstrustjohnclark.pdf
East Devon Proposed Local Plan Consultation 2012