(1)Section 90 of the principal Act (removal of alien patients etc.) shall not apply to any patient unless he is detained pursuant to—
(a)an application under section 26 of the principal Act or section 12 of the [1961 c. 15 (N.I.).] Mental Health Act (Northern Ireland) 1961;
(b)a hospital order under section 60 of the principal Act or section 48 of the said Act of 1961; or
(c)an order or direction under either of those Acts having the like effect as such a hospital order.
(2)The Secretary of State shall not exercise his powers under the said section 90 in the case of any patient except with the approval of a Mental Health Review Tribunal or, as the case may be, of the Mental Health Review Tribunal for Northern Ireland.
(3)Where the Secretary of State exercises his powers under the said section 90 in respect of a patient who is detained pursuant to a hospital order under section 60 of the principal Act and in respect of whom a restriction order is in force, those orders shall, notwithstanding section 95 of that Act, continue in force so as to apply to the patient if he returns to England and Wales at any time before the end of the period for which those orders would have continued in force.
(4)In paragraph (b) of the said section 90 for the words " a mental hospital or institution within the meaning of the Mental Health (Northern Ireland) Act 1948 " there shall be substituted the words " a hospital within the meaning of the Mental Health Act (Northern Ireland) 1961 ".