Common Travel Area
If you enter the United Kingdom through Ireland, you will pass through passport control at your port of entry into Ireland, but you will not be required to clear UK passport control. However, you will only be limited to a stay of 90 days in the UK and Ireland (or whatever the passport control officer in Ireland gives you a leave to remain for) if you qualify for a visa exemption, not the usual six-month stay in the UK for visa-exempt nationals. Hence, especially if you attempt to enter the UK as a Student Visitor (. a visitor studying for up to 6 months), you should not transit through Ireland unless you possess a valid UK visa or entry clearance permitting a stay of more than three months or intend to stay in the UK for fewer than three months.