4. In cases falling within sub-paragraph (a) above, the premises are ex hypothesi incapable of beneficial occupation. In these cases no difficulty arises because, if the steps provided for by the existing law are duly taken, liability to rates will cease as from the date of destruction. It will be necessary to review the value of the hereditament as appearing in the valuation list, and the machinery of revision - by proposal or, in London, by provisional lists - ought to be put into operation as soon as possible.