Officer may exercise discretion and allow you pass through the UK on your way to another country outside the Common Travel Area (the UK, the Channel Islands, the Isle of Man and the Republic of Ireland collectively form a common travel area)
without a visa providing that you:- arrive at a UK port on a ship and leave on the same ship within 24 hours; or
- arrive and leave by air within 24 hours and have no intention of staying in the UK (you can travel by rail or road between two airports);
and
- have a confirmed onward booking that will leave within 24 hours of your arrival in the UK.