(1) Subject to this Act, the weekly rate of disablement pension shall be increased by the amount set out in Part IV of the second Schedule if, as a result of the relevant loss of faculty, the beneficiary is incapable of work and likely to remain permanently so incapable.
(a) For the purposes of this section, a person may be treated as being incapable of work and likely to remain permanently incapable of work, notwithstanding that the loss of faculty is not such as to prevent him being capable of work, if it is likely to restrict him to earning not more than such amount as may be prescribed.
(b) In paragraph (a) the reference to "earning" includes a reference to receiving any remuneration or profit derived from gainful occupation.
(3) An increase of pension under this section (in this Chapter referred to as "an unemployability supplement") shall be payable for such period as may be determined at the time it is granted, but may be renewed from time to time.