The Secretary of State may by order require transit passengers to hold a transit visa.
"Transit passengers" means persons of any description specified in the order who on arrival in the United Kingdom pass through to another country without entering the United Kingdom; and "transit visa" means a visa for that purpose.
The order—
may specify a description of persons by reference to nationality, citizenship, origin or other connection with any particular country but not by reference to race, colour or religion;
may not provide for the requirement imposed by the order to apply to any person who under the 1971 Act has the right of abode in the United Kingdom;
may provide for any category of persons of a description specified in the order to be exempt from the requirement imposed by the order;
may make provision about the method of application for visas required by the order.