4(1)Where the prisoner has not attained the age of 21 years at the time the warrant containing the relevant provisions is issued and the relevant provisions include provision equivalent to a sentence under section 6 or 8 of the [1982 c. 48.] Criminal Justice Act 1982 (youth custody and custody for life)—
(a)subsections (1) to (7) of section 12 of that Act (accommodation of persons sentenced under section 6 or 8) shall not apply in relation to the prisoner ; and
(b)the prisoner may be detained-
(i)in a youth custody centre,
(ii)in a remand centre, or
(iii)in a prison,
as the Secretary of State may from time to time direct.
(2)Where—
(a)at the time the warrant containing the relevant provisions is issued the prisoner is not less than 16 years of age but has not attained the age of 21 years, and
(b)the relevant provisions include provision equivalent to an order imposing detention under section 207 or 415 of the [1975 c. 21.] Criminal Procedure (Scotland) Act 1975 (restriction on detention of persons under 21 years of age),
the provisions of those sections which require that, in certain circumstances, a person shall be detained in a specified type of institution shall not apply in relation to the prisoner, and the prisoner may be detained—
(i)in a young offenders institution, or
(ii)in a prison,
as the Secretary of State may from time to time direct.