20 hours Layovers at Heathrow and Dublin airports. Do I require transit visa for both?

I hold an Indian Passport.

I am traveling from Mumbai to Washington DC via the British Airways flight which has two layovers: 16 hours in London and 4 hours in Dublin. I possess an F-1 US student visa. I would be reaching London at 18:25 p.m. and would depart for Dublin at 6:30 a.m. the next day. Similarly, I would reach Dublin at 8:00 a.m. and depart for Washington DC at 12:00 p.m.

I would also need to change terminals at Heathrow from Terminal 5 to Terminal 2.

I wanted to know whether I would require a transit visa for both the places as I am not able to get proper information about the requirements from the official pages. Reading the pages only show that you can transit without a visa if you hold an itinerary to your destination and hold the visa for the US.

Please help me as I am confused and don't want to get in trouble at international airports.

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Is transit visa required for connecting flight in Heathrow?

Re: Is Transit Visa Required at London(Heathrow) Airport? "You usually only need a transit visa if you want to leave the airport as you have a long layover." Nope.

Can I transit through Dublin with UK visa?

You will remain airside and pass through an immigration checkpoint, but not pass through Border Control into Ireland. They will check your passport, your visa status for the UK and your boarding pass for your connecting flight.

Do we need transit visa for London from Ireland?

You might need to apply for a visitor visa to travel through the UK to get to the Channel Islands, the Isle of Man or Ireland. You'll usually need to apply for a Standard Visitor visa unless you're exempt. You do not need a UK visitor visa if: you have a valid visa for the Channel Islands or the Isle of Man.

Do I need a visa to transit through Dublin airport?

A transit visa does not permit you to enter Ireland for any purpose. It only permits you to transit through Ireland in order to reach your destination in another state. If the intention is to leave the port at any stage they must apply for a short stay visa in the normal way.

Do you really need Transit Visa for UK

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