The following paragraph shall be inserted after paragraph (b) of section 38 (3) of the 1972 Act—
“(bb)to any planning permission for development consisting of the winning and working of minerals which is granted (or deemed to be granted) subject to a condition that the development to which it relates must be begun before the expiration of a specified period after the completion of other development consisting of the winning and working of minerals which is already being carried out by the applicant for the planning permission.”.