A body which is authorised under section 3 or 4 of the [1982 c. 50.] Insurance Companies Act 1982 to carry on insurance business which is investment business and carries on such insurance business in the United Kingdom is an authorised person as respects—
(a)any insurance business which is investment business; and
(b)any other investment business which that body may carry on without contravening section 16 of that Act