Permitted development rights don't include sub-dividing a flat above a shop

In a recent appeal case, the planning inspector supported a council in refusing to give a lawful development certificate to a property owner who had divided an existing flat above a shop into two flats. Currently it is possible under recent changes to the General Permitted Development Order (GPDO) to convert retail space above a shop into two flats without needing planning permission. Prior to the changes, there had been the flexibility to create only one flat. In this appeal case, there was already a single flat above the retail premises. The owner appears to have taken the view that the new permitted development rights would allow him or her to convert the flat into two units producing the same result as if the space above the retail premises had previously been in retail use. However, as the GPDO does not refer to a building of mixed retail and residential use then the inspector agreed with the council that there were no permitted development rights and therefore there could not be a certificate of lawful development. This seems to comply with the letter of the law (as quite rightly it should) but not necessarily the spirit of it and it would be interesting to know what the response would be if the owner now submits a planning application for the conversion. It is worth noting that if the single flat had previously been in retail use, then the owner could have gone through the more tortuous route of first returning it to retail use (which might mean no more than using it for storage for a temporary period) and then converting it into two flats. This is because the GPDO allows reversing of the conversion from retail to residential (i.e. allows conversion back from residential to retail without needing planning permission - providing the flat had previously been in retail use). Presumably this avenue was not available because the flat had never previously been part of the retail use.