3(1)This paragraph and paragraph 4 below shall have effect with respect to the duration of existing patents after the appointed day, and in those paragraphs—
(a)" old existing patent" means an existing patent the date of which fell eleven years or more before the appointed day and also any patent of addition where the patent for the main invention is, or was at any time, an old existing patent by virtue of the foregoing provision ;
(b)" new existing patent" means any existing patent not falling within paragraph (a) above ; and
(c)any reference to the date of a patent shall, in relation to a patent of addition, be construed as a reference to the date of the patent for the main invention.
(2)Sections 23 to 25 of the 1949 Act (extension of patents on grounds of inadequate remuneration and war loss) shall not apply to a new existing patent.
(3)The period for which the term of an old existing patent may be extended under section 23 or 24 of that Act shall not exceed in the aggregate four years, except where an application, for an order under the relevant section has been made before the appointed day and has not been disposed of before that day.