Renew Land Developments Limited, in concert with social housing provider Cartrefi Conwy Cyf, sought planning permission to build 80-100 homes on a 4.4-hectare site at Plas Gwilym Quarry, Old Colwyn, Conwy, in north Wales.
However, its application was refused by Conwy County Borough Council in October 2017.
That decision was upheld by Welsh ministers' planning inspector Kay Sheffield in August 2018, principally on the basis that the development would, in conflict with a local planning policy, result in the unacceptable loss of 0.85 hectares of designated informal open space.
Her decision was, however, subsequently overturned by Judge Keyser QC at the High Court and the planning application was sent back to the Welsh ministers for fresh determination.
In his ruling, the judge noted that the open space concerned was not in public ownership and there was evidence that, even if planning permission were refused, the developer "both could and would" fence it off to prevent public access.
The inspector, the judge said, "did not adequately explain how it could be that a development that was acceptable in principle under policies in favour of residential development on suitable sites within urban areas could be rendered unacceptable on account of a policy for the preservation of open spaces, in circumstances where the inspector accepted that the landowner both could and would fence the relevant land, and thereby remove it from the stock of available open space, if the development were not permitted."
Overturning the judge's decision at the Court of Appeal today, Sir Stephen Richards said it had been common ground before the inspector "that the land was open space for the purposes of the policy" and she had therefore been entitled to proceed on that basis.
The fact that the owner of the 0.85 hectares could exclude the public from it at will did not mean that it was anything other than open space, he ruled.
Sir Stephen, who was sitting with Lords Justice David Richards and Phillips, added: "I can see no basis for the judge's view that land cannot be open space to which the policy applies if the landowner has the power to exclude the public from it at will.
"The policy protects against the loss of open space as a result of development. When planning permission is sought for a development, the policy must be applied to the open space existing at the time of the decision whether to grant permission."
It was true that if the landowner used permitted development rights to fence of the 0.85 hectares, thus excluding the public, it would at that point cease to be open space. But the judge concluded: "That is for the future. It does not affect the existing status of the land as open space or the present application of the policy to it.
"The inspector was entitled, in my view, to deal with the matter in the way that she did, proceeding on the basis of the parties' common ground that the 0.85 hectares was open space for the purposes of (the policy)."
The Welsh ministers also succeeded in other grounds of challenge to the judge's ruling. The appeal was allowed and the inspector's decision to refuse planning permission restored.
Welsh Ministers v Renew Land Developments Limited
Case Number: 2019/0898