read this for official advice, the weird bit is why someone from NI would want to do it.
with the new volatile delta strain accounting for 99% of new infections in the uk, it is no wonder that we would have restrictions on people coming from there. perhaps the op is hoping that by using the back door, they can escape the N ireland restrictions?
Due to Aer Lingus and Sobart issues I thought my flights from belfast would be cancelled and booked Ryanair from Dublin without remembering I am flying from an area with different restrictions. A stupid knee jerk reaction. Thanks everyone for your help. I am hoping I can arrange to keep the Aer Lingus flights (times have changed which presents a problem) and I can change the Ryanair to a later date when hopefully things will be better.