21. A person who, on arrival in the United Kingdom—N.I.
(a)passes through to another country or territory without alighting from the conveyance by which they arrived in the United Kingdom, or
(b)alighted from the conveyance by which they arrived in the United Kingdom for the sole purpose of continuing a journey to a country or territory outside the common travel area and
(i)remains within their port of entry until their departure from Northern Ireland, or
(ii)travels directly from their port of entry to another port of departure in Northern Ireland.