"(1) Except as otherwise provided by or under this Act, where a person is not a British subject - (a) he shall not enter the United Kingdom unless given leave to do so in accordance with the provisions of, or made under, this Act; (b) he may be given leave to enter the United Kingdom (or, when already there, leave to remain in the United Kingdom) either for a limited or for an indefinite period; (c) if he is given limited leave to enter or remain in the United Kingdom, it may be subject to all or any of the following conditions, namely - (i) a condition restricting his employment or occupation in the United Kingdom; (ii) a condition requiring him to maintain and accommodate himself, and any dependants of his, without recourse to public funds; and (iii) a condition requiring him to register with the police. "(2) The Secretary of State shall from time to time (and as soon as may be) lay before Parliament statements of the rules, or any changes in the rules, laid down by him as to the practice to be followed in the administration of this Act for regulating the entry into and stay in the United Kingdom of persons required by this Act to have leave to enter, including any period for which leave is to be given and the conditions to be attached in different circumstances; … . "(3) In the case of a limited leave to enter or remain in the United Kingdom, - (a) a person's leave may be varied, whether by restricting, enlarging or removing the limit on its duration, or by adding, varying or revoking conditions …;"
"(1) Where a person arriving in the United Kingdom is refused leave to enter, an immigration officer may, subject to sub-paragraph (2) below - … (c) give … [the owners or agents of the ship or aircraft in which he arrives] directions requiring them to make arrangements for his removal from the United Kingdom in any ship or aircraft specified or indicated in the direction to a country or territory so specified being either - (i) a country of which he is a national or citizen; or … (iv) a country or territory to which there is reason to believe that he will be admitted. "(2) No directions shall be given under this paragraph in respect of anyone after the expiration of two months beginning with the date on which he was refused leave to enter the United Kingdom except that directions may be given under sub-paragraph (1) …(c) after the end of that period if the immigration officer has within that period given written notice to the owners or agents in question of his intention to give directions to them in respect of that person"
"Although the power which is given to the Secretary of State in paragraph 2 to detain individuals is not subject to any express limitation of time, I am quite satisfied that is it subject to limitations. … as the power is given in order to enable the machinery of deportation to be carried out, I regard the power of detention as being impliedly limited to a period which is reasonably necessary for that purpose. The period which is reasonable will depend upon the circumstances of the case. What is more, if there is a situation where it is apparent to the Secretary of State that he is not going to be able to operate the machinery provided in the Act for removing persons who are intended to be deported within a reasonable period, it seems to me that it would be wrong for the Secretary of State to seek to exercise his power of detention. "