‘Fraid we’re not talking about anything sparkly here. No, this is to do with the commencement of development. You might wish to make note of a distinction highlighted by an inspector in a recent appeal (DCS Number 200-007-575).
“… the case law which culminates in Orange PCS v Islington establishes that a permitted development right crystallises when commencement occurs. This right will not therefore be lost if a new development order comes into force.”
“In the case of prior approval, the rights crystallise when the prior approval is granted or deemed to be granted by the Council, not when development has commenced.”
More detail can be found in paragraphs 18 and 19 of the decision.
Section 4.34 of DCP Online concerns permitted development.