Where the Secretary for Justice or the Prisons Parole Board considers that the conduct of any person serving a sentence of imprisonment, not being a sentence of life imprisonment, has been exemplary during his sentence, or where any person serving such a sentence has during his sentence performed some outstanding act of service, the Secretary or the Board may recommend to the Minister that the person be granted, in addition to any remission which may be granted to him under subsection (1) of this section, a special remission of part of his sentence, not exceeding one-twelfth of the term, and the Minister may, if he thinks fit, direct that a special remission be granted accordingly. Any such direction may be revoked by the Minister at any time before the person is released.”