Developer Gladman Developments Limited wants to build 290 new homes on a 15.2-hectare site adjoining the Grade 2 listed Orleton Hall outside Telford.
Telford and Wrekin Borough Council refused Gladman's application for the proposed development in December last year.
The council said the project would be an "unacceptable encroachment into the open countryside", eating up a large expanse of high quality agricultural land.
It also said the development would "adversely effect" Orleton Hall's parkland.
However, a planning inspector allowed Gladman's appeal and granted planning consent.
While expressing no definite view, he said he "doubted" that the council had a five-year supply of deliverable housing land.
The impact on the hall's grounds would be "less than substantial", he added.
And he underlined the public benefits of the "sustainable" project, including 73 affordable homes.
One of the decisive factors, however, was the inspector's finding that some of the council's housing policies did not conform to the National Planning Policy Framework and were "out of date".
The council challenged the inspector's decision at the High Court in London, but has had its complaints dismissed by Mrs Justice Lang.
The inspector's conclusions in relation to local housing land supply and the impact on the character and appearance of the hall's park and gardens could not be faulted, nor could his view that the development would be sustainable, the judge ruled.
The council had failed to show that the inspector's conclusions were wrong in law or irrational, she concluded.