In determining whether an outbuilding at a house in Buckinghamshire would be permitted development under Schedule 2, Part 1, Class E of the GPDO an inspector made reference to the leading court case on the subject, Emin v Secretary of State for the Environment and Mid-Sussex DC .
The inspector explained that in a case such as this (DCS Number 400-029-565), it was held in Emin that the appellant is expected to identify the purpose and incidental quality of what is proposed in relation to their enjoyment of the dwellinghouse and answer the question as to whether the proposed building is genuinely and reasonably required or necessary in order to accommodate the proposed use or activity and thus achieve that purpose.
The appellant argued that the provisions of Class E are generous and, as the appeal site was within his ownership, he could do as he wished, within reason and staying within legal parameters. Again, however, the inspector explained that, as found in Emin, the incidental use cannot rest solely on the unrestrained whim of the appellant himself. In the inspector’s view, the appellant’s example of a large building to accommodate antique steam rollers would fall within the context of an unrestrained whim, even if such a building could fall within the size limitations of paragraph E.1 of Class E.
Well, we’ve narrowed it down.
Emin v Secretary of State for the Environment and Mid-Sussex DC  is cited in a number of appeal cases referenced at section 4.3445 of DCP Online.