'321. The following grounds for the cancellation of a person's leave to enter or remain which is in force on his arrival in, or whilst he is outside, the United Kingdom apply: (i) There has been such a change in the circumstances of that person's case, since leave was given, that it should be cancelled.'
'If the Secretary of State considers it objectionable that those who have been given leave to enter as students are not pursuing their studies, the appropriate course would seem to us to be to take steps to remove them for that reason. At present the appropriate way of doing this would seem to be to curtail, under Section 3(3)(a) of the 1971 Act and paragraph 323 of HC 395, the period for which the student has been given leave to enter, and then to remove the student under Section 10 of the 1991 Act. The former step would give rise to the right of an in-country appeal.'
'(a) Having only limited leave to enter or remain, he does not observe a condition attached to the leave or remains beyond the time limited by the leave.'