"(3) The Secretary of State may by order provide that, in such circumstances as may be prescribed – (a) an entry visa, or (b) such other form of entry clearance as may be prescribed, is to have effect as leave to enter the United Kingdom."
"4(3) … it shall have effect as leave to enter the United Kingdom on one occasion during its period of validity; and on arrival in the United Kingdom the holder shall be treated for the purposes of the Immigration Acts as having been granted before arrival leave to enter the United Kingdom: (a) in the case of an entry clearance which is endorsed with a statement that it is to have a effect as indefinite leave to enter the United Kingdom, for an indefinite period; (b) in the case of an entry clearance which is endorsed with conditions, for a limited period, being the period beginning on the date on which the holder arrives in the United Kingdom and ending on the date of expiry of the entry clearance."
"298. Indefinite leave to remain for the spouse of a person present and settled in the United Kingdom is to be refused if the Secretary of State is not satisfied that each of the requirements of paragraph 287 is met."