(1)If it appears to the Secretary of State that a person serving a sentence of imprisonment is a person to whom this section applies, he shall, by notice given to such person in accordance with paragraph 2 of Schedule 1 to this Act, place him under supervision under that Schedule on his release from prison.
(2)Subject to the provisions of subsection (4) thereof, this section applies—
(a)to any person serving a sentence of imprisonment for a term of three years or more ;
(b)to any person serving a sentence of imprisonment for a term of not less than six months,
but less than three years, who is under the age of twenty-six years at the commencement of the sentence ; but does not apply to a person serving a sentence of imprisonment for life.
(3)The Secretary of State may by order substitute a lower limit of three months instead of six months in paragraph (b) of subsection (2) above.
(4)This section shall not apply to persons serving a sentence of imprisonment commencing before such date as may be prescribed by order of the Secretary of State under this subsection ; and any such order may prescribe different dates in respect of sentences described in paragraphs (a) and (b) respectively of subsection (2) of this section, and, in respect of sentences comprised in the said paragraph (b), either according to the length of the term of imprisonment under a sentence or to the age of the person on whom it is passed.