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You do not need a Transit visa if:
You have an Indian passport; and
you arrive and depart by air have a confirmed onward flight that leaves on the day you arrive or before midnight on the day after you arrive have the right documents for your destination (eg a visa for that country); and
youβre traveling from the Republic of Ireland and itβs less than 3 months since you were last given permission, on the basis of holding a valid Irish biometric visa, to land or be in Ireland
(GOV Website)
If you do not meet all of these requirements, you will need to apply for a Visitor in Transit Visa.