If the Secretary of State is satisfied that a person serving a sentence of imprisonment is under twenty-one years of age and might with advantage be detained in a Borstal institution he may, after consultation where practicable with the judge or presiding chairman of the court which passed the sentence, authorise the Prison Commissioners to transfer him to a Borstal institution ; and the provisions of the next following section shall thereupon apply to him as if he had on the date of the transfer been sentenced to Borstal training:

Provided that if on that date the unexpired term of his sentence is less than three years those provisions shall apply to him as if he had been sentenced to Borstal training three years before the expiration of that term.

If a person detained in a Borstal institution is reported to the Secretary of State by the board of visitors to be incorrigible, or to be exercising a bad influence on the other inmates of the institution, the Secretary of State may commute the unexpired part of the term for which the said person is then liable to be detained in a Borstal institution to such term of imprisonment as the Secretary of State may determine, not exceeding the said unexpired part; and for the purpose of this Act the said person shall be treated as if he had been sentenced to imprisonment for that term.