removal of PD for external alterations prior to part 40 coming into force. - Public forum - Planning Advisory Service (PAS)

My query is whether a condition removing PD on an application that was granted prior to Part 40 and which removed PD for roof alterations, extensions, and goes on to specify no external alterations could be capable of also preventing solar panels. The reason I ask this is that there have been a couple of instances in my Authority where solar panels have been put on re-occupation dwellings and barn conversions where we have said that as PD had not been removed under part 40 (as Part 40 did not then exist) then permission was not required. This clearly is at odds with the decision that was made at the time where the Authority had sought to gain control over any future external alterations. At the time, we would have considered that solar panels required planning permission and therefore there would have been no requirement to specifically specify that solar panels were not allowed. My question is therefore, that if we have a pre part 40 removal of PD that specifies removal of the classes that relate to roofs, extensions etc. and also goes on to clarify that pd is removed for external alterations of the building, then could that be considered to override the provisions of part 40 and mean that planning permission would be required for Solar Panels on the roof?