Notwithstanding anything in section 3(5) or (6) above but subject to the provisions of this section, a Commonwealth citizen or citizen of the Republic of Ireland who was such a citizen at the coming into force of this Act and was then ordinarily resident in the United Kingdom—
(a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b) shall not be liable to deportation under section 3(5) if at the time of the Secretary of State's decision he had for the last five years been ordinarily resident in the United Kingdom and Islands;
(c) shall not on conviction of an offence be recommended for deportation under section 3(6) if at the time of the conviction he had for the last five years been ordinarily resident in the United Kingdom and Islands.
A person who has at any time become ordinarily resident in the United Kingdom or in any of the Islands shall not be treated for the purposes of this section as having ceased to be so by reason only of his having remained there in breach of the immigration laws.
The "last five years" before the material time under subsection (1)(b) or (c) above is to be taken as a period amounting in total to five years exclusive of any time during which the person claiming exemption under this section was undergoing imprisonment or detention by virtue of a sentence passed for an offence on a conviction in the United Kingdom and Islands, and the period for which he was imprisoned or detained by virtue of the sentence amounted to six months or more.
Nothing in this section shall be taken to exclude the operation of section 3(8) above in relation to an exemption under this section.