“(i) The Secretary of State must intend to deport the person and can only use the power to detain for that purpose; (ii) The deportee may only be detained for a period that is reasonable in all the circumstances; (iii) If, before the expiry of the reasonable period, it becomes apparent that the Secretary of State will not be able to effect deportation within that reasonable period, he should not seek to exercise the power of detention; (iv) The Secretary of State should act with reasonable diligence and expedition to effect removal. Principles (ii) and (iii) are conceptually distinct. Principle (ii) is that the Secretary of State may not lawfully detain a person “pending removal” for longer than a reasonable period. Once a reasonable period has expired, the detained person must be released. But there may be circumstances where, although a reasonable period has not yet expired, it becomes clear that the Secretary of State will not be able to deport the detained person within a reasonable period. In that event, principle (iii) applies. Thus, once it becomes apparent that the Secretary of State will not be able to effect the deportation within a reasonable period, the detention becomes unlawful even if the reasonable period has not yet expired.”
“…the Home Secretary’s exercise of the statutory power to detain a prospective deportee until the making of the deportation order or until his removal or departure is not unfettered. It is limited in two fundamental respects. First, it may be exercised only for the purpose for which the power exists.”
“… may be exercised only during such period as is reasonably necessary for that purpose. The period which is reasonable will depend on the circumstances of the case.”
“The question in every case in which it is alleged that a decision-maker has failed to have regard to the factor identified in the statute is whether the decision-maker has in substance had regard to the matter identified. In the written decision produced by the decision-maker he does not have to refer, expressly, to the relevant statutory duties; however, the terms of the written decision must be such that it is clear that substance of the duty was discharged.”
“in discharging immigration and/or asylum functions concerning children, the best interests of the child will be a primary consideration; it will not be the only consideration, but the use of the word primary means that it will always be at least an important consideration.”