(1)In section 12(1) of the principal Act (interpretation of Part I) in the definition of " relevantly appropriated " (which, among other matters, excludes oil appropriated for production purposes) after the word " purposes " there shall be added the words " in relation to that or any other oil field " .
(2)This section has effect, and shall be deemed to have had effect, for chargeable periods ending after 31st December 1977.