Paragraph 4
Where there is a substantial change in the operation of an existing Part A installation on or after 31st October 1999 and before 1st January 2001, the prescribed date for that part of the installation affected by the change shall be—
where an application for a permit authorising the operation of that part of the installation is duly made before 1st January 2001, the determination date for that part of the installation;
where no such application is made, 1st January 2001.
Where there is a substantial change in the operation of an existing Part A installation on or after 1st January 2001, the prescribed date for that part of the installation affected by the change shall be the date on which the change is made if earlier than the date which would be the prescribed date for the installation under paragraph 2.