Making sense of the various permitted development rights for change of use under Part 3, Schedule 2 of the GPDO is a long way from easy. In particular, many have drawn the conclusion that a local planning authority which fails to determine a prior approval application within the requisite period has granted permission by default. Not so, as we highlighted in No worries.
In dealing with an appeal concerning a residential barn conversion in south Yorkshire under Class Q (DCS Number 400-022-642) an inspector has confirmed that the decision in Keenan v Woking BC and SSCLG  makes it clear that if an application for prior approval is submitted for works that do not fall within the scope of permitted development, and the council fails to issue a decision within the specified period, the works do not become permitted development.
Helpfully, the inspector has set out the judge’s reasoning verbatim: “The sole and limited function of this provision, (the need for prior approval), was to enable the LPA to determine whether its own “prior approval” would be required for those specified details of that “permitted development”. If the authority were to decide that its “prior approval” was not required, the condition would effectively have been discharged and the developer could proceed with the “permitted development” – though not, of course, with any development that was not “permitted development”. If, however, the authority failed to make a determination within the 28-day period, again the developer could proceed with the “permitted development”, but again not with any development that was not “permitted development”. The developer would not at any stage have planning permission for development that was not, in fact, “permitted development”. “
As we understand it, then, a proposed development must have the required characteristics of permitted development under Part 3, inherently and intrinsically. Otherwise, it’s a non-starter.
Section 4.3423 of DCP Online sets out Part 3 permitted development rights.