"Like any other question of construction, this [whether a rule change applies to all undetermined applications or only to subsequent applications] depends upon the language of the rule, construed against the relevant background. That involves a consideration of the immigration rules as a whole and the function which they serve in the administration of immigration policy."
"the question is what the Secretary of State intended. The rules are her rules."
"In the exercise of their functions under this Act immigration officers shall act in accordance with such instructions (not inconsistent with the immigration rules) as may be given them by the Secretary of State . . ."