The case concerned a collection of red-brick mansion blocks known as Portman Mansions, in Chiltern Street, W1, which has 120 residents.
The Portman Mansions Residents Company Limited wished to install a one-storey basement development, comprising an estate office, meeting rooms and a residents' gym.
The roof of the building was to be planted with vegetation, including semi-mature trees, and its retaining wall would be no higher than an existing wall.
Objections were, however, received from the Trustees of the Placemount Pension Fund, who held a long lease in respect of a lower ground level flat within Portman Mansions, on the basis that the new wall would be just 0.8 metres from the premises' bay windows.
The trustees said that the development would reduce the amount of daylight reaching the flat, which was used as offices, would have an overshadowing effect and would increase the sense of enclosure within the premises.
Planning permission was, however, granted in April 2016 by a Westminster City Council planning officer, to whom the decision was delegated. A previous planning consent for an effectively identical development had been granted in 2013, but not implemented.
In overturning the 2016 consent, Judge John Howell QC ruled that the reasons given for the officer's decision were inadequate.
He ruled that there was no indication that the trustees' amenity objections had been considered on their merits before planning permission was granted, either in 2013 or 2016.
The officer had mistakenly proceeded on the basis that those objections did not constitute a reason for refusing permission as consent had already been granted for the development.
There was no evidence that the officer had appreciated that the new wall would be only 800mm from the flat's bay windows.
The judge concluded that that error had infected other aspects of the decision and no proper consideration had been given to a development plan policy intended to discourage developments that would lead to unacceptable overshadowing or loss of natural light.
The planning permission was quashed.
R on the Application of Shasha & Ors v Westminster City Council. Case Number: CO/2910/2016