Lowther Castle and its gardens, in Cumbria, have been closed for 70 years and currently stand inaccessible and buried in vegetation.
Architect Feilden Clegg Bradley, garden designer Dan Pearson and landscape architect The Landscape Agency have already been involved in the project for several years.
The Lowther Castle & Gardens Trust plans to transform the imposing remains of the Gothic castle, its massive stables and more than 20 hidden gardens through the restoration.
Land Use Consultants will focus on understanding and conserving the surviving 17th century gardens.
Principal Dominic Cole told HW he expected to work closely with the Landscape Agency, Dan Pearson and Feilden Clegg Bradley to develop the plans over the next three months.
"The whole tender process has taken a year and now we need to start planning what is really going to happen," added Cole. "I have never seen anything quite so big or classy in the UK as the 17th century structure."
For more on this story, see Horticulture Week magazine on 15 January.
Subscribe to Horticulture Week for more news, more in-depth features and more technical and market info.