Control of areas near protected monuments

Nothing contained in any notification under sub-section (1) shall affect any building, structure or other work above ground or any alteration or extension thereof, if it was constructed, erected or executed before the date when notice of intention to issue a notification was given under sub-section (2), and for the purpose of this provision a building, structure or other work and any alteration or extension thereof shall be deemed to have been constructed, effected or executed before that date – (a). if its construction, erection or execution was begun before that date, or (b). if and so far as its construction, erection or execution was necessary for the purpose of performing a contract made before that date.