3. After section 11(1) there shall be inserted the following subsection—
“(1A) A person arriving in the United Kingdom through the tunnel system shall for the purposes of this Act be deemed not to enter the United Kingdom unless and until he has left the tunnel system, and, subject to subsection (1) above, a person who has not otherwise entered the United Kingdom shall be deemed not to do so as long as he is detained, or temporarily admitted or released while liable to detention, under the powers conferred by Schedule 2 to this Act.”.