If you pass through border control, you'll need a UK transit visa unless you're exempt. You’ll need to pass through UK border control if you: 1. Leave the main airport building 2. Collect and recheck your bags 3. Your onward flight departs on a different day than your arrival 4. There's no place to stay overnight in the airport. You may not need a transit visa if: - You arrive and leave by air with a confirmed onward flight before midnight the next day. - You're traveling to/from Australia, Canada, New Zealand, or the USA and have a valid visa or residence permit from those countries or the EEA. - You have a valid Irish biometric visa or a US Permanent Resident card. Always check with your airline if you're unsure about passing through border control.