QBD 19 October 1987. Application to quash decision of SoS who refused planning permission for a residential development . At issue was whether the land should be kept open, or whether it could be released for building. In assessing the balance between housing demand and supply, the SoS, in his decision letter, followed a mathematical formula laid down in DoE Circular 30/85 . Para 1.17 of the circular deals with housing land requirements and states that once the time period of the structure plan provisions for housing had expired "...the 5-year housing land requirement should be taken as 5 times the average annual housebuilding rate in the period covered by approved structure plan housing policies". The developers contended that the paragraph`s guidance was ambiguous. It was not clear whether it referred to the annual housebuilding rate actually achieved, or that predicted in the structure plan. Held, that SoS`s decision letter was insufficiently clear as to the mathematical calculati