The 250-year-old sketch, found in a drawer by present Kirkharle Courtyard owner John Anderson, is now taking form in the landscape.
Work was due to begin several months ago on the £100,000 lake and tree planting project envisaged by the young Capability Brown, but required further public funds in order to do so.
Now work on the lake has been given funding from Natural England, Northumbrian Water, Northumberland County Council and other partners.
The Forestry Commission is also backing the project with a grant of £4,000, which will finance the planting of between 3,000 and 4,000 foot-high saplings in three distinct blocks.
John Anderson came across the precious drawing in the drawer of a desk owned by his grandfather, Major George Anderson, in 1980.
The plan was later authenticated by landscape experts at Newcastle University, where it is now on permanent display in the library.
A turf cutting event was organised to mark the start of the landscaping work last week.
The scheme is expected to be complete in March 2010.
Subscribe to Horticulture Week for more news, more in-depth features and more technical and market info.