If the owner of a building on or to whom a notice referred to in subsection (1) was served or delivered, fails to resume or to complete the erection of such building within the periods specified in such notice or, when applicable, within such periods as extended in accordance with subsection (2), and the local authority in question
is of the opinion that such building is unsightly or dangerous to life or property or derogates from the value of adjoining or neighbouring properties, such local authority may by notice in writing, served by post or delivered, order such owner to demolish such building, to remove the material of which such building consisted and any other material or rubbish from the site in question, and to otherwise clean up such site within the period specified in the last-mentioned notice.